Last updated: 12/24/2016

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PressurePro Tire Monitor System

We have been using a tire monitoring system since shortly after we started fulltiming in 2000. It has saved us from problems on numerous occasions by allowing us to catch tire inflation problems before they resulted in a blowout. It has been argued that if you check your tires every morning you don't need a monitoring system. I used to believe this too, until I picked up "road hazards" between checks (I check tires every time I stop) which caused catastrophic tire failure due to heat buildup from low pressure. Believe me, unless you are very lucky, just the damage repair savings from one bad blowout will more than pay for a tire monitoring system. Also consider, if you have a motorhome, that you will likely not know if you have a blowout on the toad. Even with the camera on it is likely that the first indication of a problem will be when the rim and tire overheats and starts smoking. The peace of mind provided by the monitor is worth it to me.

Until the summer of 2004 we used a SmarTire system, which we really liked. The SmarTire system we had monitored up to 6 tire positions, and wirelessly transmits temperature and pressure for each position. It worked well, but its weakness is the number of positions it will support. We needed to monitor the tractor, as well as 6 positions on the trailer. This prompted us to look for a system that would support more than 6 tires. Another thing I disliked about SmarTire was it's inability to report over 127psi (this may have been corrected on later versions). On high pressure trailer tires (110psi) you can easily exceed the 127 psi limit in hot weather. [Note: As of 2005 SmarTire has a monitor system available that supports the number of wheel positions we would require. ]

There are two basic types of tire monitor systems available: those that attach to the valve stem (like PressurePro), and those that place sensors inside the tire (like SmarTire). There are pros and cons to both types of systems. The largest negative to the internal systems is the difficulty and expense of installation. SmarTire, although difficult to install, does report internal tire temperatures as well as pressure. If you think you would like this feature, they are worth checking out.

There are a number a systems on the market that support 12 or more tire positions, and use the valve stem sensor to transmit pressure information. However, until PressurePro was developed there were significant issues with each of the systems; in my mind, at least.

Some systems require relays on the trailer and truck, since they will only transmit a short distance. Even SmarTire required that we install an auxiliary pickup antenna on the rear of the truck, due to the overall length. Some systems require transmitters to be custom built for a specific tire pressure. This means you can't move the sensor from the trailer to the truck. This also means you can't decide to upgrade tires on the trailer from (say) E rated tires (at 80psi) to G rated tires at 110 psi. Or even to change the inflation pressure based on loading.

PressurePro has the following desirable characteristics:

  • it will monitor up to 34 positions, so it is expandable by buying additional sensors.
  • the sensor installs on the valve stem, so it is trivial to install (anyone, even the mechanically "challenged" can do it). No rebalancing is required on most vehicles.
  • each sensor is independently programmed by the user for the position it is used in. Tire pressure is easy to change simply by taking the sensor off, adjusting the tire pressure, and replacing the sensor.
  • the sensors can be moved to any position.
  • tire rotation is simple.
  • the pressure range reported is up to 150 psi.
  • the transmission range of the sensors is suitable for a 40' motorhome with a toad, or a 40' trailer, pulled by a tractor, without adding an external antenna. Some units do require the external antenna or repeater. If you are towing doubles, or have some specific "dead" spots with the standard antenna either the repeater or the external antenna will resolve this. We had no problems with reliable reception without the antenna when we were just towing the trailer.
  • an optional external antenna or a repeater is available if needed, but that is unlikely.
  • the system reports pressure every 5 minutes, EVEN IF you are still. This means you can check the truck and trailer in the morning before you pull out simply by running through the display. You don't have to start moving to activate the sensors just to find out you have a low tire you might have liked to top up. And you don't have to manually check the tires with a gauge.
  • it is easy to separate the tow and towed vehicle without causing false alerts because some tires are "missing". You can move the display between the tow vehicle and the towed vehicle, like you might want to do in a motorhome.
  • the display is very thin and can be mounted anywhere with Velcro (see the picture for my mounting location).



  • the sensors do not have a removable battery. They are sealed units and need factory service when dead (about a 3-4 year lifespan if in continuous use). You do not have to pay $50 for a new sensor; the factory will send you replacements for about $30 and will mail them before receiving the old one back. This is a brand new sensor - not rebuilt or just a new battery inserted - and has all the latest technology in it.
  • because the sensor installs on the valve stem you should probably use metal valve stems. But you should be using them anyway.
  • on small passenger car tires there might be a balance problem. This is easily resolved with 3 oz of weight opposite the valve stem.
  • the sensors are easily removed, so MAY be subject to theft. This would be true of any valve stem sensor.

Balancing all the pros/cons, I think that PressurePro is still the best valve stem system available (as of 2009).

You can find additional info at the  Pressure Pro website.

For a comparison of the features of the various brands of monitors available (as of November 2006) you can download the Excel file Tire Monitor Comparison. Although this is now somewhat dated, the comparison will give you things to think about as you evaluate the available brands.

A final note on the PressurePro system: there are other valve stem tire monitors on the market that sell for less. One thing to consider in evaluating those against PressurePro is the history of the company, and service after the sale. New products always have quirks associated with them. Working out these issues takes time. PressurePro has gone through all this already, has the reputation for providing outstanding service, and they have been in business for quite a while. If needed, they will get you a new sensor very quickly, and will work with you directly if you have issues. I can tell you from personal experience that a simple phone call had a new sensor to me within 2 days when I had a sensor damaged from a road hazard. And there was no charge - although I would not count on not being charged.  Sometimes the cheapest system is not the best way to go. This technology is maturing and there are products other than PressurePro that work well. Just be sure that you have a source of service for the product you buy.

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Truck Electrical Additions

Truck Wire center labeled.jpg (94536 bytes)This section describes the wiring center I added to  my Volvo 610 tractor. Most of this is generally applicable to any truck - the Volvo-specific parts are obvious. Building large cables yourself, and general electrical practices/tools are covered in the RV Electrical/Solar section under Wiring.

The purpose of the wiring center is to supply 12 /120-volt power for the cab, and to the trailer plug for the 5th wheel. This article covers the basic how to's along with resources for parts and accessories. The wiring practices described here are commonly used and are code conforming to the best of my knowledge, but this document should not be taken as electrical advice - it is simply the way I did it.

My wiring center is in the driver's side compartment, on the forward (left) wall. It is built on top of ¾ plywood, which was glued to the plastic walls of the compartment with construction adhesive. Use of the plywood simplifies installation of components and permits use of cheap, commonly available fasteners without penetration of the compartment walls. I painted the wood black before installation - this provides a more pleasing appearance. To protect the terminals and wires from shorts and damage, two plexiglass panels cover the appropriate areas of the walls. This prevents cargo in the storage box from impacting the wire center. The plexiglass is mounted with ¼ x 3.5 lag bolts through ½ plastic pipe used as standoffs. The area over the inverter is not covered to ensure proper heat dissipation. The wire center is shown in the picture above without the plexiglass panels in place. The perspective is looking forward from the rear of the truck.

All wiring is fed into the compartment from a 3" x 1" hole in the floor. The easiest way to do this is with a 1" drill bit - drill a hole at each end of the cutout, and use a Dremel tool with a cutting blade to connect the holes. The hole is a little crowded - you may want to consider a slightly larger hole.

Trailer Light Converter and Brake Controller

volvo_rv_connection.gif (16314 bytes)The trailer light converter provides power and signals to the 5th wheel. You need the converter because a semi-trailer has separate brake/turn signals and the RV trailer has combination brake/turns. The trailer connector lines you will tap in the tractor have to have the signals modified - the converter is what does this. Using a converter properly combines the signals, isolates the tractor from the trailer electrical system, and is self-powered so you can not overload the tractor circuits when you add more lights to the trailer. On older tractors you can wire the trailer directly off the tractor tail lights, but this is a bad idea. It will increase the chances of future problems. Newer tractors (from around 2003 and newer) have computer controlled lighting circuits that monitor the load on the circuit. These can not be tapped, since the lighting computer then thinks there is a "problem" with the additional load. You can find additional wiring diagrams on Mark Bruss's website in Trailer Wiring.

The JackalopeeAt the time I modified my truck I used a Hoppy Model 46255 converter to supply the appropriate signals. This is a powered converter - the advantage is that it isolates the truck electrical system from the trailer, preventing any shorts in the trailer from impacting the truck. There have been enough issues with the 46255 that I would no longer use it. IF I was going to use a Hoppy, I would only use the Hoppy 46365, which can handle 8 amps. The Hoppy converter is the gray box directly below the inverter in the picture of the truck wiring center at the top of this section. Look in the Resource Listing section for sources for the Hoppy.

A far better alternative to the Hoppy is now available. Shown to the left, the ET Jackalopee is a custom tailight converter available from Szmyt ET Hitches and Custom Design. It provides for full isolation of the tractor from the trailer, and is capable of handling up to 60 amps per line. It is a far superior solution to any other available on the market, and is now the only one I would use. The instructions that come with the Jackalopee are very complete, and explain the entire trailer lighting control system better than any previous documentation I have seen.

In my wiring, the inputs to the converter come from the existing green Volvo trailer feed wire, which was originally terminated behind the cab. This was disconnected and moved into the storage box, through the hole in the floor. Turn signals and brake light feed were picked up from the original trailer connector. The brake light signal was fed forward (with a 14-gauge wire) into the cab to act as the brake signal for the brake controller. It was easier to pick the brake signal up here than to find the brake signal in the cluster of wires in the Volvo fuse center, and since you have to run a wire back from the controller anyway, it was no additional work. The braking output from the brake controller is returned to the drivers compartment on a 10-gauge wire to the wire center, where it is soldered to the new trailer connector line, which then runs to the rear of the truck. This brake line feeds 12v power to the trailer braking system and needs to be at least 10 gauge to minimize voltage drop. Any connection in this line needs to be soldered, or you will loose too much voltage.

One additional note on the trailer lights: You might want to consider fusing the turn/running light output lines from the light converter. This will protect the converter from shorts in the trailer. Otherwise, you might damage the converter when you have a short in the trailer. It is cheap insurance, since no matter what converter you use you will have more than a few dollars tied up in it. And you do not want to have an issue with a destroyed converter on the road.

There are two ways to proceed on the brake controller, depending on what type of brakes the trailer has: standard electric drums, or hydraulic disc brakes. Typically, both types of brakes are actuated with an electric signal from the truck - both the truck and the trailer use an electrical signal to run the brakes. The reason for this is so any truck can pull any trailer (in theory).

With conventional drum brakes the electrical signal is sent back to the trailer by the brake controller, and actuates the magnets on the drums directly. This leads to lots of issues; primarily, bad connections in the electrical connectors that drops the voltage too low causing a lack of current at the brakes. Wires that are too small will do this too; you need 10 gauge wires all the way to the brakes. The end result of a pure electrical system is often marginal braking on the trailer because the magnets are not running at optimal power.

With disc brakes, the trailer has hydraulic brake actuation, since electrical means of directly clamping the pads would be ineffective. The electrical signal from a conventional brake controller in the truck is sent back to the trailer, and then converted to hydraulic pressure via the electric/hydraulic actuator which interfaces to a master cylinder just like on a car. This works as well as the electrical signal feeding the actuator, so your braking effectiveness is somewhat dependent on the quality of the controller used in the truck. Some electric/hydraulic brake systems require specific controllers to interface with their actuators. You need to check with your trailer brake manufacturer to ensure your controller of choice will work well with your hydraulic trailer brakes.

The issue with all electrically-based controllers is that they do not predict the braking force requested by your foot on the pedal well - a LOT is lost in that "translation". A superior method of translating the braking request to the brake actuator is to directly tap into the air brake system of the tractor. This is the only method of getting true proportional braking. All "pure electric" methods only simulate proportionality via pendulums or gyroscopes, although the gyroscopic method is quite good. I originally used a Prodigy controller, which worked OK. A Prodigy is an advanced pure electric controller that uses pendulum technology. It is probably the best of the pendulum controllers. A few years later I moved to the Hensley TruControl Gold, which works as well as can be expected of a controller that is not integrated into the truck braking system.  The Hensley uses gyroscopic technology to sense deceleration of the vehicle. It is far superior to the Prodigy and other pendulum controllers.

If I was to do this over again and wanted to maintain an electrical braking signal from the truck to the trailer, I would use an air-over-electric proportional controller; the Hayes-Lemmerz (#100400-B ). Most of the wiring would be the same except for picking up the brake line signal. The major difference is that these controllers tap a brake air line to give you true proportional braking with the air brake system of the truck, instead of using the electrical brake signal.

The Hayes uses a mechanical servo tapped into the air line that directly detects the amount of brake application. brakesmart1a.jpg (74519 bytes)brakesmart2a.jpg (78763 bytes) The best place to pick up the signal for the air/electric controllers like the Hayes is in the "stop" air line, behind the instrument panel.  These controllers allow the Johnson Bar (the handle on the dash) to be used for trailer braking. You can get the Hayes KH100400B Air Actuated Brake controller at various outlets. There used to be two other controllers on the market that operated like the Hayes - tapping the air line. Both MaxBrake and BrakeSmart are no longer in business.  Hayes is your only option for an air/electric controller at this time.

I now use a BluDot brake actuator in the trailer. It does not require a brake controller, since it operates directly off the truck air system via the gladhands on the truck, just like a semi-trailer connection. From an operational and function perspective this is the best system available - the truck and trailer operate as a SINGLE unit. Like anything else, there are pros and cons to using a BluDot. You can find an article on my BluDot installation in the RV Improvements section.

Truck Wire center labeled.jpg (94536 bytes)This drawing shows an overview of the trailer converter wiring.  It shows the logical connections between the existing Volvo trailer cable, and the new trailer cable being added. I mounted all of my connections in the storage box. I  used terminal strips to attach the wiring and transition to the converter. This has several advantages: 1) it allows you to move the wires around, if you get them wrong the first time 2). it makes for a neater installation 3) it allows you to add auxiliary lighting (like LED stop/turns) on the rear of the truck cab and keep it isolated from the tractor system. Make sure you rub some Oxguard onto the wires before crimping on the terminals.

Wire Runs

All of my wires run from the storage box, down through the floor, and then forward under the cab. They are strapped to the existing wire bundle that is attached to the frame. They re-enter the cab just forward of the drivers seat, just inward of the removable floor trim plate through several small holes drilled in the cab floor. They proceed forward to the front of the truck under the floor mat, and from there either up to the top of the dash, or through the dash, as appropriate to their function. Some wires run along the top of the dash down by the defroster outlets in black split loom. You don't see them in that position. These wires are the camera wires for my backup cameras, and the telephone cable that controls the remote On/Off for the inverter. The brake signal (input) and return (output) wire from the brake controller are run inside the dash to the controller which sits just to the right of the drivers right knee.

A note about penetrating the floor: this is fine in the metal floor of a Volvo, but if you have a Kenworth or Peterbuilt make sure you do not have the balsa wood cellular floor - this can not have holes cut in it without reinforcing them properly. Use the holes the manufacturer supplied.

You could also run the wires forward into the engine compartment and bring them through the firewall through a grommet. I found it easier to bring them in at the door jamb.

The 120 volt AC line that feeds the receptacle on the dash runs on the opposite side of the truck routed under the mat in a similar fashion, except that it comes through the rear of the storage compartment, behind the refrigerator (which sits behind the passenger seat), and then under the floor mat. I ran the 120-volt power on the opposite side of the truck so that its proximity to the camera line would not cause interference.
The 12-volt System

The wire center is supplied with 12-volt power directly by the inverter cables. The inverter cables terminate in distribution hubs at the wire center, which allows you to easily tap power for various functions. All negative wires terminate directly onto the negative distribution hub. There are no terminations to the chassis - this will prevent bad grounds in the future.

Blue Sea 12 Circuit Fuse Block.jpg (8568 bytes)Just to the left of the inverter is a small 12-volt fuse center. I acquired it from Wrangler, but you can find similar fuse centers at good auto parts stores. Blue Sea makes a very nice fuse center (shown at left) with either a 6 or 12 circuit capacity. This has a negative bus incorporated into it. The part number for the 12-position is 5026 (Fuse Center). My fuse center currently contains the Hoppy converter fuse, a fuse supplying a relay for my bed-mounted backup lights, and a fuse for the 12-volt supply for the cameras. The backup lights are tapped from the tractor cargo light switch, so when I activate the light on the back of the cab, the lights built into the back bumper also come on.

You can add a negative 12-volt buss bar if you need one (you won't need it if you spend the few $ for the Blue Sea panel shown). Use a buss bar from an AC load center. These are available in the electrical section of Home Depot or Lowes, and are used to add neutral and ground busses to load centers. Just screw it to the plywood and you are ready for hookups. Use a neutral lug and 4 or 6 ga cable to tie it to the distribution hub. You could buy a negative buss bar from a specialty catalog - these have the advantage of having a post to tie in the negative feed line. They also cost upward of $99, depending on what you get.

Future expansion of the system is much easier with the fuse center in place (I have learned this the hard way).

In the cab, the brake controller is supplied with 12-volt power from the distribution hub on the firewall, directly above the steering adjustment pedal. Ground  is tapped directly off the battery, following the installation instructions. Alternatively, you could tap the negative post behind the steering adjustment pedal, but the controller instructions are specific about tapping the battery directly. Both the ground and the positive are 10 gauge wire - overkill, but I had it.

Trailer Connector Pin Diagrams - 7-way

To the left are the wire locations of the RV 7-way connector. You must go by position of the wire relative to the notch - not just by color, since there is no standard for the colors of wires. The general layout is as follows:

LH Stop & Turn
Electric Brakes
RH Stop & Turn
Tail Running Lights

In my installation the new trailer wire harness is supplied with 12-volt power for the trailer battery bank (position 4 in the diagram) from the distribution hub in the storage compartment. Typically, you would tap the output of the alternator to supply the trailer line. You would use a battery isolator or a solenoid to separate the banks - really only required if you keep the trailer and truck plugged together for long periods. If you really want to get fancy you could use a "smart" charging switch, or a cross-charge regulator in place of an isolator or solenoid. This would ensure that both the truck and trailer battery banks get a full charge off the alternator. If you don't use a "smart" charging switch then the alternator will shut down when the first battery bank reaches the cut-off voltage of your truck regulator. This will leave the other bank (typically the trailer bank) without a full charge. NEVER use a battery A/B/Both switch. These just cause problems and if not used correctly can cause a system-wide electrical surge (if you switch it wrong while the alternator is running) that will burn out your alternator diodes and/or other truck electrical components.

In my application these are all unnecessary. Since I have a large solar system (480 watts, 29 amps), I find that satisfactory for my trailer battery bank charge. I only want access to 12-volt power at my trailer plug in order to run 12-volt appliances (like a 12-volt water pump for pumping water from the truck to my trailer when boondocking). You will probably want to tap your alternator output if you depend on the tractor to charge your trailer battery bank. Using the tractor battery bank as the charge source for the trailer bank will result in the trailer bank never being fully charged.

On the dash behind the CB radio holder I added a three outlet 12-volt accessory receptacle. This is handy for the GPS, etc. This is permanently tapped off of the CB power point, from behind.

A side note on the Volvo electrical monitor: Many Volvo's have an electrical monitoring system designed to cut off power to various electrical items when battery voltage falls below a designated threshold. An alarm goes along with this. On my Volvo, along with many others, this alarm would go off even when voltage was "normal". In doing the work above, I discovered that the alarm was grounded to the rear of the power center. Removing the ground wire stopped the alarm and does not seem to have any side effects. You may, or may not, have the same wiring set-up.

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The 120-volt System

Truck_electrical_center_simple.jpg (44914 bytes)You have a choice to make when you design your 120-volt system. First, you can build a minimum system that meets your electrical needs. Most people only run a refrigerator, occasionally use a microwave, and TV/satellite/DVD. The electrical requirement to support these devices is minimal, especially if you use an LCD TV. So you really don't need an expensive or fancy system. Figure out your electrical requirements by checking your devices for their power requirements; add up the wattage of all your devices that will run at the same time. Add at least 40% to that and you know what size inverter you need. Typically, that would be 1200-1500 watts, or less.

Truck_electrical_center_combined.jpg (52178 bytes)The second system is more sophisticated and permits more future expansion. It includes a larger inverter that incorporates a charger and auto switch. This permits you to expand the system to include a separate house battery bank, and to run higher-powered devices for longer periods of time. This system approaches the capabilities of an RV system typically used with a solar setup. The advantage of using the inverter/charger is that the auto switch capability makes your 120-volt wiring much simpler. It also costs significantly more!

I chose to go the lower-cost route. Mainly because I do not envision using my truck as an RV for long periods of time without shore power hookups. So my 120-volt inverter needs directed me to the lower cost inverter. This drove the rest of the electrical design. I will describe the details of my implementation, but I have also included a schematic and details of the more sophisticated implementation. Mark Bruss chose to use a high-powered inverter with his Volvo 770. You can see the details of his electrical center at Mark Bruss' website.

The inverter I used is a Xantrex XPower 1200 (1000 watts, continuous) with the optional remote control. I purchased this online, through At the time, they had the best price (around $170 for both). I chose the 1200 because the highest power appliance I intend to power is a 600-watt microwave, and this inverter has adequate power to do it. There is also an XPower 1750 (1500 watts, continuous) available; it uses the same remote control.

If you want an integrated inverter/charger/transfer switch then the Tripplite APS2012 would be a good choice. They run around $600 online; you will also want the $105 remote switch. (Prices are approximate at the time of this writing.) The integrated inverter/charger/auto switch costs more, but makes the wiring a little simpler.

Ideally, any inverter you choose should be direct wire (for both AC and DC) and should have a remote on/off switch. Direct wire for the AC output circuit simplifies the wiring to your house loads. If your inverter has outlets, most likely all of the rated output is available from any of the outlets. Just use a 12 ga extension cord (cut to the appropriate length, or a direct-wire plug) to supply the 120-volt power to either your 120-volt junction box, or loadcenter.

The remote on my inverter (and most of them) uses a 4-wire telephone cable. It attaches to the back of the inverter. The control panel on mine happens to be the same height and brushed aluminum finish as the Eaton Autoshift display, so I removed a screw from the Eaton panel and mounted the remote right on it. If you don't know differently, it almost seems like it belongs there.

A note on inverter technology. All the inverters above are modified sine wave. You may hear that using anything but a pure sine wave inverter will cause interference problems with TV's or that certain devices won't run at all. While this is certainly possible, depending on the device, modern modified sine wave inverters run almost all devices "cleanly". I would not hesitate to use a modified sine wave inverter for everything except very specialized applications. Some TV's will not work with modified sine wave - but I have never seen one, and I have installed many inverters in both RV's and vehicles. Oxygen concentration equipment, laser printers and certain battery chargers all need pure sine wave. Almost all other devices work fine on modified sine wave.

Microwave ovens will run at reduced output on all inverters, so you simply program more time into them. We find it is best to run microwaves on "high" only. Microwaves of all varieties are sensitive to the DC input voltage. Less DC voltage, less cooking. This is true even though the AC output voltage of the inverter is held fairly constant. Don't plan on cooking extensive meals with your microwave - it is best used for re-heating only.

DPDT 30 amp relay used to auto-switch to shore power. Click on these to enlarge.

Transfer_relay_x.jpg (42708 bytes)

Iota 30 amp transfer switch
Iota_30_amptransferswitch.jpg (8680 bytes)

My inverter is mounted upside down for access to the lugs. To the right of the inverter is a 30 amp DPDT relay with a 120-volt coil. Any good electric supply house should have them. The relay takes as input the 120-volt inverter output and the shore power line. The shore power also feeds the coil, so when shore power is available it will always be favored. A cover is available for the relay, and I recommend spending the extra $20 to get it. I covered the entire area with a plexiglass panel so the power lugs are protected, but the relay cover would probably be better. The relay cost $27 without the cover.

An alternative to "building your own" transfer switch from a relay is to simply buy a transfer switch. Iota makes a good one at a reasonable price. A 30 amp version is $55 at If you are going to buy the cover for the DPDT relay like I used, just buy the transfer switch instead; you will be better off.

Of course, if you are using the higher-priced inverter/charger with an auto switch capability you will not need to set up your own transfer switch - it is built into the inverter.

Block heater receptacle used as Shore Power input
Shore_power_connector_x.jpg (16872 bytes)
Rated for 20 amps

The shore power connector is shown to the above. In my case, the original conversion used a 20 amp block heater connector, which was adequate for my loads (I plug into 20 amp power sources, either on the side of my RV, or the receptacles in the RV power post). If you supply a 30 amp shore power input, use the appropriately rated shore power connector. A twist-lock marine connector would be a good choice - see for a good selection of parts. Even if you use a 20 amp connector like on my truck, the wire from the shore connector to the 30 amp relay should be 10 gauge, in order to support a full 30 amps. If you wire it this way from the outset, you won't have to upgrade this later if you decide to increase your power input and switch to a 30 amp connector.

Plugging your truck directly into an outlet on your RV: If you do this, you need to figure the effect it has on total RV power draw. For example, if we plug our trucks block heater into the outlet on the side of our rig (instead of directly into the RV park power outlet), we can easily trip a 30 amp breaker. If you are using an electric heater in the RV, and a few other things, the 12 amps that the block heater draws can push you over the 30 amp rating.

If you store your truck for long periods of time and want to keep your batteries charged via your shore power hookup the simplest way to do it is to use a 120-volt trickle charger. Wire the feed for this onto the relay where the shore power line attaches. Make sure you maintain polarity if the charger requires it. Wiring to the input side of the relay will ensure that the charger only draws its power from the shore power hookup, never from the inverter. An alternative (and maybe better) wiring strategy is to put a receptacle into the shore power line inside the compartment, but before it goes to the relay. Then, simply plug the trickle charger into the receptacle. The output from the trickle charger ties directly to the distribution posts - cut the battery clamps off, and replace them with ring terminals. You want to make sure you tap into power before it enters the inverter - you don't want to try to charge batteries with the inverter output from the batteries. Again, this is not required if you use the inverter/charger, because the charger is built into the inverter. I use the BatteryMinder Plus Model 12117 which is a battery maintenance charger/desulfator. It only has 1.0 to 1.33 amps output, but for maintenance charging that has proved to be sufficient for my four battery bank. The more powerful Model 12248 (2,4,8 amp charger) may be a better choice for some, but it costs far more.

In my installation the output from the transfer relay goes to a 4 inch electrical junction box where it is split into 2 lines. The first goes to feed the refrigerator and microwave. It is routed through the back of the storage compartment, wire wrapped to the existing wire bundle. Instead of mounting a receptacle in/on the passenger-side storage compartment, I used a direct-wire multistrip, which I mounted above the blower inside the passenger-side storage compartment. The plugs for the refrigerator and microwave enter this compartment through a hole behind the refrigerator. This was easier and just as effective as a wall-mounted receptacle. I specifically did not want a receptacle because I wanted the refrigerator to be flush against the side of the storage compartment - with a receptacle the plug would have interfered with flush mounting. I also did not want to see any cords in the cab area.

120-volt Loadcenter
Truck_120_Loadcenter.jpg (60537 bytes)
Use with 30-amp shore power input

Instead of using a junction box to originate your 120-volt wire runs, you can alternatively put in a 120-volt load center. If you use the higher-powered inverter/charger, or have a 30-amp shore power input this will be required, because you will not have adequate overload protection on your truck circuits without it. (If you restrict yourself to a 20 amp input you have properly sized breakers at the power source. With 30 amp input your truck wires could become overloaded, since the source breaker is 30 amps and your internal wire runs are probably wired with 12 or 14ga.) Size the load center to support the number of circuits required for your application. Like the junction box, the input to the breaker box (load center) is the output from the transfer relay (either the separate relay, as in my installation, or the relay inside the auto switching inverter/charger which just passes through shore power when it is detected). A schematic of the breaker box is shown above.

Truck Wire center labeled.jpg (94536 bytes)The second 120-volt line follows the first one through the storage compartment, through the hole, behind the refrigerator, under the floor mat, and up onto the truck dash. There it terminates in a standard shallow duplex box (painted black). I use this for my laptop computer (no, I do not have a 12-volt adaptor for it).

A note about the refrigerator. I decided not to use a 12-volt fridge. Mainly because of the cost - over $500. I found a small Whirlpool  120-volt energy efficient refrigerator for $58 at Lowes that only draws 1.1 amps AC. The battery bank can easily sustain the 12 amp DC load this fridge places on it (remember, you loose power during conversion). I don't run it that much when not on shore power, or driving. The additional advantage of this refrigerator is that its width permits it to fit between the seat belt mount and the bed, and its height permits the passenger seat to recline some. After living with this refrigerator for over seven years I am still very pleased with it. It cools down extremely fast, and I can leave it on for days at a time on the inverter with no apparent effect on the battery bank. When looking for a refrigerator there are two important characteristics: the amp draw, and the width. Look for a fridge that is 18" or less, or you will have trouble fitting it behind the passenger seat in a Volvo 610/630.

Ground the inverter following the manufacturer's instructions. If you are using an inverter with a transfer switch, the AC ground input and output lines have lugs or ground wires inside the inverter to attach to. If you are using a small inverter and its inbuilt receptacle then the AC output line ground is simply part of the wire you plug in. Internal to the inverter, it is likely bonded to the chassis.

Almost all larger inverters have a separate external chassis ground lug on them. This goes directly to chassis ground - NOT to the DC negative buss bar, or the battery ground, or the AC load center. Usually, 6 AWG wire is sufficient, but the inverter manufacturer will specify the wire size depending on the inverter size.

The AC output from the inverter goes to some sort of AC distribution panel (or junction box, if not protected by breakers). In the case of smaller inverters without an inbuilt transfer switch you will run it through an external transfer switch or relay to control shore power selection.

If you are using an external transfer relay like the Iota, follow their instructions on grounding hookup. There will either be bonding terminals inside the transfer switch, or they will specify the method that the grounds be bonded to each other.

If you are using a DPDT relay, like I did, then bond all the grounds together. If you use a wire nut, make sure you tape it. You can see this in the picture of the DPDT relay (follow the green wires). Establish a chassis ground either where you merge the grounds (add an extra chassis ground wire to the three existing ground wires) , or at the AC distribution panel or box, depending on how you prefer to wire. When not connected to AC shore power the chassis ground will offer some protection, but it is nowhere near as good as an earth ground. When on shore power, ground will flow back to the utility ground.

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Adding a Separate House Battery Bank to the Truck

Truck_house_bank.jpg (62823 bytes)If your electrical needs are great (or if you think they are) you have no alternative but to add a separate house battery bank to your vehicle. We are talking about electrical usage while not connected to any charging source – e.g. the engine is not running, and you are not hooked to shore power. The starting battery bank will suffice for occasional boondock use, but is not designed to be deeply cycled. If you deep-cycle your starting bank more than a couple of times, you will be buying batteries sooner than you had planned.

Adding a separate house bank solves the problem of overburdening your starting bank, but creates its own set of issues – mainly cost and complexity. A lot of cost, and a lot of complexity. In order to have a properly functioning house bank you need to have a charging source for it. Deep cycle batteries are more sophisticated than starting batteries and require a multi-stage charger in order not to “kill” them over time. Using just your alternator with its stock regulator will result in a constant undercharge – remember, that alternator/regulator is designed to maintain starting batteries, which are rarely discharged more than 5%, and have a different charge curve than deep cycle batteries. Fortunately, if you are implementing a house bank you are probably already using an inverter/charger which is designed to manage deep cycle batteries. So you will have a way of fully charging your house bank when hooked to shore power.

Adding a separate battery bank for your "house" loads means you have to:

  1. Provide for a primary charge method – this is your inverter/charger.
  2. Provide for a means of charging while not connected to shore power – via your alternator.
  3. Isolate the starting and house banks electrically, while still allowing a charge from the alternator. You have a choice here – a solenoid, a simple battery isolator, a “smart” isolator, or a multi-output regulator that has a separate charging algorithm for the house bank. There are variations of each category, but these cover the major groups.
  4. Provide instrumentation, so you know what your house bank is doing; when to stop drawing it down, when to charge it, when it is in trouble. Without instrumentation you will eventually kill your bank, since you will never know its charge state.
  5. Determine the type of battery to use; flooded cell, AGM, etc. I highly recommend a simple 6-volt lead acid golf cart battery, available at Sam’s Club for around $65 each. If you can convincingly argue that an AGM or other type is better, or that 12-volt batteries are better, then you don’t need to be reading this. I recommend the lead acid because if you screw up your bank they are cheaper to replace. Consider them as your training wheels. If you have the need, and get to the point where you can manage your batteries well, then you might switch to a more sophisticated battery technology. Bring money, though. You need to use 6-volt batteries hooked in series-parallel. There are many discussions on the net about using banks of 12-volt batteries instead of 6-volt. Don’t do it. There are many reasons why – do your own research if you want. Or just take my advice and buy 6-volt golf cart batteries and be happy with your system.
  6. Determine the size (in amp-hours) of the house bank. To do this you need to know your electrical requirements while without a charging source (boondocking) – how long will you watch TV, how much will you use the coffee maker, the microwave, etc. You can calculate the requirements of each appliance from the electrical plate on them. Add in any 12-volt lighting that is tied to the house bank. Then add around 15-25% to that.
    Here is the rule of thumb for battery use: never use more than 50% of the amp-hours in the bank. Figure normal electric usage as 25% of the bank, that way you can go several days without negatively affecting your battery bank. This applies to deep cycle batteries only – NOT to starting batteries. A standard 6-volt battery pair, hooked in series for 12-volt will have an amp-hour rating of 200-220, depending on the battery (we will use 200 for this example). So if you have a bank of four 6-volt golf cart batteries you have 400 amp hours total, of which 200 is available for use. This is going to be more than enough for almost all peoples needs, assuming you are just supplying the truck, and not an RV as well. We boondock for months at a time in our 5er with a bank that size, and use our sat TV, microwave, coffee maker, etc. Of course, we fully recharge with solar each day. We rarely see more than 100 amp-hours of deficit – but you can now see the importance of instrumentation. Otherwise, how do you know what you used? So, I recommend a 4-battery bank. A 2-battery bank would suffice for most people, but 4 will cover any extra requirements in the future.

You need to decide where to put the batteries. Use your imagination, but remember, it is best to keep the wire run to the inverter as short as possible. Definitely not farther than 10’, max, which includes twists and turns to get there. If you have more than 5’ of run, use 4/0 cable, despite what you might read in your inverter manual. Actually, I always use 4/0 for any inverter over 1700 watts. You also need to make sure the inverter is not in the same enclosure as the battery bank. Batteries are explosive devices – inverters have relays and other electrical components in them. Batteries also outgas while charging. You don’t want your inverter in the hostile environment of a battery. Also, when locating the battery box, make sure it is easy to service the battery bank. You will need to check fluid level at least once a month, especially if the house bank is heavily used.

BattDist 1.jpg (98923 bytes)The picture to the left shows a very sophisticated electrical distribution system. In this case the distribution center is co-located with the battery bank. This is an elegant and expensive design.


Charging the Truck House Battery Bank

We already know that we need a 3-stage charger to properly maintain the house bank. Fortunately the inverter has such a beast, so you have a good charge source when plugged in. What about while driving?

An automotive alternator, along with its regulator, is designed to charge a starting battery bank. When you add the house bank there is no method to add a separate charging circuit to the existing regulator to independently charge the house bank. It is simply not designed for that. In addition, you don’t want your house loads to draw down your starting battery. That requires that the house and starting bank be isolated from one another when you are using power, but that they be combined when the alternator is supplying power for recharging.

The one thing you never want to use to combine banks is a cheap A/B/ALL battery switch. You WILL forget to properly switch it, and if done improperly it will destroy your alternator, and probably much of the computer electronics in your vehicle. Don’t use it unless it has starting isolation to protect your circuits. You also need to make sure it is rated for the expected loads.

The simplest way to combine (and by combine, we are talking for charging purposes, not for starting) the banks for charging is with a simple high-power relay (at least a 150 amp normally open). When the engine is running the relay is closed and charge output from the alternator goes to both banks. When the engine is off, the relay opening isolates the banks. Under $40, but you will never get a good charge on the house bank. That is because the starting bank will probably come up to full charge first, and the regulator will shut the charge down to both banks. Remember, the regulator knows nothing about two banks. This might be OK if you intend to plug into shore power often and use the high-power charger in the inverter to maintain the house bank.

An alternative, and a better solution, is to use a solenoid with a charging controller integrated with it. There are various models on the market. The logic in the controller maintains and manages the charge to both banks, based on various settable conditions. It is acting as a smart charge regulator. Some of these even have temperature compensation. They are not cheap however. Expect in the $150+ range, depending on features. Take a look at the Ample Power Auto switch. A disadvantage to all types of relays/solenoids is that they can fail. In some cases they can also push a high voltage surge through the system, although this is rare.

You could also use an isolator with a diode built into it. The typical reason not to use a diode-based isolator is that they consume about .5 to 1.5 volts while active. This lowers the voltage to the banks and results in never obtaining a full charge. If you use an isolator with a Schottky diode instead of a silicone diode you will eliminate most of this loss. At 100 amps, expect to loose around .45 volts with a schottky-based isolator, and around .8 volts with a silicone-based isolator. The isolator is a much better, but a relatively expensive, solution at around $140+ depending on features (they go up fast). Hellroaring makes an advanced isolator with minimal voltage drop. Check out the BIC-85150A for around $150. Again, if you know you are going to correct this charge deficit with shore power, a low cost isolator can be an adequate solution. A regular old cheap isolator rated at 150 amps should be around $70 or less.

Blue Sea also makes an ML-Series automatic charging relay that will do a good job. It will charge either or both batteries and has a charge sense line for both. It can also safely combine the banks for starting purposes, and has no voltage drop on charging. Most important, it has battery bank isolation, so that during starting you do not put shock loads or surges into the house systems. This comes with a remote panel.

Also look at the devices and monitors made by National Luna. They make expedition equipment typically used to monitor dual battery systems in Jeeps and other "expedition" vehicles.

Another alternative, although I doubt most of us need it, is to replace or augment the existing regulator with a dual output regulator with inbuilt 3 stage charging. There are various capabilities and alternatives here. You will get a great charge, but expect to pay $400+ by the time you set up your system properly.

I recommend something like the Ample Power Autoswitch, The Blue Sea relay, or the Hellroaring isolator. It is a good compromise between cost and functionality. It will give you a good charge, protect your batteries, and is relatively simple to install.
Instrumentation of the House Battery Bank

Without a way to determine battery state-of-charge you are risking killing your batteries. You also don’t know how much energy is available for your use. Any system using a separate house bank without a battery monitor is an incomplete system, and typically is not going to be satisfactory in anything but trivial use – in which case, you should question why you have a separate house bank.

There is only one critical measure, and that is ampere hours. An amp-hour meter measures amps consumed and amps restored. It is like a fuel gauge on your vehicle. All quality battery monitors have an amp-hour function. They also measure voltage, and some have a simplified “fuel gauge”-like display that gives a quick reading of battery charge state (half full, ¾ etc.). You use the meter for various things – finding the ampere consumption of an appliance while in use, determining the amount of charge going back into the battery via the charger or alternator, condition of the batteries (by how much charge they will accept), and most importantly, how “full” your battery is. If you have 200 amps max to use, and you microwave something (say 4 amp hours) and brew a pot of coffee (12 cups, say 33 amp hours), and watch an LCD TV for an hour (about 8 amp hours), plus you have a phantom draw (more on that later) of 8 amp hours (per day) you now know, through the meter, that you have a deficit of 53 amp-hours. This is well within the 25% rule (which would be 100 amp hours on a 400 amp hour battery bank). If you did not have the battery monitor, you would never know.

A note about phantom loads. Every system has consumption even if nothing is “on”. This is called the phantom load. It comes from various things like “instant on” TV’s, charging bricks, inverters left in standby, microwave displays, and just electrical “leakage”. You need to determine the phantom load on your system using the amp hour meter – the phantom load adds up fast over a one or two day period.

Shunt.jpg (4706 bytes)To measure amp hours, the battery monitor uses a shunt installed in the negative line, and a remote display attached via a telephone cable, or Ethernet cable (typically). All loads have to be attached upstream of the shunt (e.g. don’t terminate your negative buss bar or distribution hub on the battery side of the shunt). Use a 500 amp shunt to get measures of hundredths of an amp. Most monitors come with an appropriate shunt, but be sure to include that in your pricing if they are extra.

Battery monitors also provide you with battery voltage, which is really only useful to observe charge stage, or to determine if the battery is really totally full or discharged. Voltage is not an accurate measure of battery state of charge in between full and empty. The reason is that voltage is only useful if the battery is at rest for 24 hrs (i.e. no load for 24 hrs.) - not a practical option in a system being used.

There is a lot more to battery monitoring than I have described here. Over time you will come to “know” your batteries, and how your system operates normally. This will allow you to quickly pick up anomalies, like marginal battery cells, before things become critical. Most of the battery monitors come with pretty good tutorials. It can be pretty overwhelming to try to learn everything at once. I would learn a little at a time, watch your batteries, and you will be surprised how soon you will understand them.

Trimetric_2020.gif (139760 bytes)There are various monitors on the market. Some of the more advanced inverter/chargers have integrated monitors that are well worth the money. The (older) Link 1000 monitor is an example.   These contain the remote switches for battery charging, and for turning the inverter on. For the inverters we have discussed here, you will have to get a separate monitor and remote panel. You can look at the monitors available, and do your own research, but I highly recommend the TriMetric TM-2020 (shown) or the RV2025 by Bogart Engineering if you need a separate monitor (separate from the inverter control functions). You should be able to get the monitor with shunt for around $160. The Xantrex LinkPRO also provides a fully-featured monitor, but it is far more expensive.

You can see that adding the separate house bank adds complexity and cost. Be sure you need it. Remember, you can always add it later. Expect to spend at least $600 over a system without a separate house bank. Plus whatever it costs you to build or buy the battery box.

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Truck Hauler Bed


Side_view_truckx.jpg (34463 bytes)In March 2004 we went to Kilgore, TX to have a custom body built for our truck. We looked long and hard for the right body builder - the right builder in our estimation is one who does custom work, very high quality, is easy to work with, has experience with our truck type, and is realistic in pricing.  We found all this and more in Herrin Welding Service, Kilgore TX.  Herrin Welding builds all kinds of custom truck bodies, from simple to complex.  They are a family owned business that can build you anything you want - their bodies are built in steel, which for a HDT is preferred, to add extra weight to the rear suspension.  You can email Herrin Welding at Their phone number is 903-984-7139 and their web site is  Those of you who know me know that I am very fussy. You won't be disappointed in Larry Herrin and his operation - give them a try. To see some other examples of Herrin truck bodies you can go to the Other Herrin Truck Bodies page of our old web site (I'll eventually move them). You can see pictures of out truck bed on our Picasa album. There are also pictures at the end of this section.
Our bed is a relatively simple design. Mainly because we have a short wheelbase and require space to carry a motorcycle or ATV on the deck. This eliminates the option of fancy vertical storage cabinets behind the cab. We need the deck space to fit in our future "toy". We have a flat deck, with two small side boxes in front of the axle, and two larger side boxes behind the axle (we had the frame cut at 39" behind the back tire to accommodate these larger boxes). We also have  two 46" wide x 4" deep lift-top tool boxes over the wheel wells.  Much like a Stalick or Highwayman bed.  I would have liked to have deeper boxes over the wheels, but with our deck height, 4" is the best we can get and not interfere with the ability to dump the air suspension. The rear treatment is a double dovetail. The hitch is in a trough, not boxed in. The trough is 9" deep - this maximizes the size of side and top storage boxes while maintaining an inch of clearance between the tire and the bottom of the saddle box when the suspension is dumped.  Even with the trailer king pin fully recessed this gives a minimum of 11" of clearance over the deck. All lights are LED's, and there are two work lights recessed into the tail controlled by the cab cargo light switch. The top is black  Line-X. There is a small (15" - front to back) removable box in the front of the bed, between the cab and the main bed. This is easily removed for servicing cab suspension components.  Mike McFall's Volvo 770 has a Herrin body on it modeled after ours, except he added drop-in boxes between the frame rails, forward of the trough. In our body that area is wasted space, because of the requirement to carry a motorcycle. I should have had a large drop-in box put there even though it would be inaccessible with a motorcycle on the deck.
We have been asked many questions about the body and its design.  After living with it for over a year, here are some random comments on it.  First, I'm still pleased with the job Herrin Welding did, and would recommend you check with them for any custom work you need done.  Second, the saddle boxes over the wheels have the locksets in the top. This causes water to sit in the handle wells, but this has not proved to be a big problem yet...the handles do leak some, but it is relatively minor, and the things I have stored in the saddle boxes are not affected by the leaks. Mike McFall had similar boxes built on his body, and his leak more than mine do. You might consider this when designing the bed. To be fair, Larry Herrin told me (and Mike) that the locks on top would leak, so it's not like we did not know what we were getting into.
One thing I would change if I were to do it over is to either shorten the rear overhang 6" or kick it up at the end.  If you get into a big dip you WILL hit the rear.  This has not proven to be much of a problem, but the change would improve the design.  We have also been asked why we did not build a tunnel box in the front (a tunnel box connects the two front boxes with a "tunnel" over the truck frame, allowing storage of long items). This would have added significant cost to the body, due to the method required to frame it. So we decided to do without. It was strictly an economic decision, but we do not miss it. Other than that, we are satisfied with the design.

One of the critical measurements is the height of the body. You have to make tradeoffs in the amount of storage you build in vs. the deck height. This  is especially true if you are going to load a motorycle with a loader. Some loaders can not be easily used on decks that are over 46" (or so) without adding additional blocking to the bottom of them. If you are winching or craning the motorcycle then it does not matter. The higher the deck, the more storage in your boxes, though, and to build in usable "saddle" boxes, as in our truck, you need at least a 49" deck height. Most trailers ride level at a 46'-47" hitch plate height. You need at least 8" clearance above the hitch plate height for the overhang of the trailer to move in turns and dips, and 10" is a pretty standard design measure. Lay it out carefully or you will not have a level ride, or will have clearance problems.

One thing I would have liked to have done, but did not, was to build in a vertical storage cabinet inside the vertical cab air foils. You have 14" of depth on a Volvo in this area (16" on a T2000), and if you extend the box out 4-5" it still looks OK. This allows a 14" - 18" deep box to be built the entire width of the cab. That is a lot of nice storage. The reason we did not do it was the desire to carry a motorcycle, which meant we had to use this space for the handlebars and mirrors given our short wheelbase.  I may still build one. If I do, the doors will be split half way up (4 doors), in order to allow the upper area to be accessed with a motorcycle on the deck. There is just barely enough space for a small motorcycle or scooter, the cabinet, and swing room for the trailer - we are talking inches here. I will also integrate LED stop/turn lights, and backup spots in the top of the cabinet. You only need 1 1/2" behind the cabinet for cab float, by the way, although I would probably go out 2".


Roddick Drom.jpg (104157 bytes)Red Rover drom.jpg (156589 bytes)The white Volvo 770 in the picture to the left is owned by Richard and Dianna Lafferty. The body was built by Larry Herrin. Their cabinet is not full width because of the vertical exhaust stack; the cabinet is "balanced" by not extending to the fairing on the driver's side. The cabinet is 83" high, 58" wide and 19" deep and has 4 fixed shelves. There are more pictures of this tractor in the Other Trucks album.

The next picture is Jeffery Roddick's T-800 with a custom drom cabinet on it. This was a working tractor, not an RV hauler, when the picture was taken - it is now an RV hauler. Note the cross storage with side access, as well as rear access to top cabinets. This drom box is 18" deep. The last picture is "Red Rover", owned by Mark and Dale Bruss. It has a standard aftermarket headache rack mounted behind the vertical air foils for stack clearance. Mark added stop/turn lights and backup lights to the cabinet. You can see more pictures of Red Rover on Mark's website

Our objective was to design the smallest truck (and bed) that we could and still carry a motorcycle. We used a relatively crude Excel worksheet to help us with the design layout and to test various scenarios. You can download this worksheet for your own use (it is in an older version of Excel so more people can use it - ignore the errors generated on newer Excel versions). It contains our 182" wb tractor, Joe Johnson's 202" wb, and a layout for a T2000  and Volvo 770 with the same body on it that we have on our Volvo. It also has a 770/780/730 layout with a smart deck. Since originally publishing this, I added a "body calculator" that allows you to play with various wheelbases and see the effect on the overall truck size. Note: this file is about 200KB  Truck body calculator and bed layout

In the pictures below, our truck is the white one. Mike McFall's maroon 770 has a bed modeled after ours. There are minor differences - the biggest difference is he added two additional "drop-in" boxes between the frame rails. I had thought of using this space, but because I intended to carry a motorcycle I thought it would be mostly inaccessible, which caused me to drop the idea. In retrospect I should have added them. They could have been used for long-term storage. Mike's hitch is dropped down between the frame rails, which you can see if you look at the pics carefully. Mike's maroon truck has a simple ledge around the back of the deck - ours is "clean" under the tailights.

Our truck - rear view

Note side angles and bumper hitch layout

Mike McFall's truck

Note difference in bumper hitch and rear step

Tom Harrison's truck

Bumper hitch totally boxed in. Note 5er hitch is boxed - not a good thing - you need the tunnel

Tom Harrison

Side view of body

Mike McFall's truck

Note the extra "drop in" boxes on his deck

Our rear boxes

We only have 1 drawer. I built these myself from wood.

Saddle box

Only 4" deep, but worth the trouble for the storage.

Note the rear box is the bigger one

Front cross box

Removable for access to cab components.

The begining of our body



Upper Bunk

Many Volvo 610's only come with a single bed. This is because they are often used for regional hauling or by a single driver, instead of being team driven. Most Volvo's that are team driven are 770's, because they have additional space in them with the larger condo.  

All Volvo's have the connection points for the upper bunk, and you can order that bunk from the dealer, if you can not find a surplus bunk. But they cost in excess of $800 by the time you buy the complete setup. The upper bunk in the  Volvo 610, 660 and 770 are the same, and the mounting hardware is the same. (The 770 cab is wider, but the bunk is the same.)

Because we overnight in our truck from time to time we wanted the extra sleeping space, but did not want to pay for an OEM bunk. We also wanted to configure the bunk so that it could be used for a backrest when in the down position. The normal bunk folds up - we wanted our bunk to fold down to the backrest position. So we decided to build our own.


Bunk2014.jpg (74850 bytes)On the back wall there are two connection points for attachment of the safety net for the bed. If you pull back the wall padding you discover that these connection points are very substantial. I decided to use them for connection of the rear support for the upper bunk. I used 2" aluminum angle to span the rear of the cab. The bunk platform rests on this when it is in the raised position. I used the original bolts (from the safety net straps) to secure the aluminum to the back wall of the cab. It is a very solid connection - I'm not worried about it collapsing at all. 


Bunk2 009.jpg (78664 bytes)Bunk2 012.jpg (102774 bytes)You have to secure the base of the bunk to the ledge that supports it somehow. I decided to use two threaded inserts and screw knobs in from the bottom to secure the back of the bunk from shifting in any direction. This worked out well. It is easy to screw them in and they hold things securely.  They are not required to be real strong - they just keep things from shifting around. I did find that I had to use a little epoxy on the inserts to keep them in place when inserted in the wood frame. If you look at the picture carefully, you will see some tape on the back of the inserts to keep the epoxy out of the threads when I insert them.

The platform is made out of wood. I originally wanted to weld it up out of 1" aluminum tubing. But I changed my mind based on the expense and trouble. Instead, I ripped 2x2" stock out of 2x4's. I built a "ladder" framework from the 2x2's - everything is air nailed and glued together. I doubled the 2x2's at the front and the back for extra rigidity. This turned out not to be necessary, but without them I thought the ladder framework was a little "floppy" before being sandwiched. I then sandwiched the ladder between two sheets of 1/4" floor underlayment - again, glued and shot with trim nails. I trimmed the front and sides in scrap 1x3" oak and painted the entire thing "Volvo gray". Total cost was under $20 - the only thing I had to buy was two sheets of underlayment. The rest was scrap material. The outside dimensions of the platform are 72 1/2" x 32 1/2". This leaves about an inch clearance to the walls on the sides, which makes it easier to raise and lower the bunk into the backrest position. 

Bunk2 010.jpg (83939 bytes)Bunk2 011.jpg (81741 bytes)Supporting the front of the bunk is a little tricky, since I wanted something that stores out of site, is strong, and is easy to put into position by one person. I used 1/2" galvanized plumbing pipe for my supports. The tops of the pipes insert into 3/4" galvanized pipe flanges secured underneath the platform at the corners. The tricky part is how to secure the pipes at the base in such a manner as to allow them to swivel for both easy placement into the flanges, and to fold down alongside the lower mattress. I used swivel casters (100 lb rating) with the wheels removed and the pipes inserted in them. This works well - it allows you to get the angle you need to orient the pipe properly when the bunk is erected, and allows you to easily swivel the pipes out of the way for storage. The casters are screwed to the plywood lift-deck that supports the bottom mattress. Depending on your bunk setup you may have to extend one side an inch to properly support the caster. Because the top platform is not as wide as the bottom mattress the pipe supports will angle in some when in the raised position. This is easily accomplished with the swivel casters.

When the platform is in the backrest position there was nothing securing the top of it - the entire thing just rested on the lower mattress. Because it was almost vertical (at about 15 degrees) it could flip forward pretty easy, as my dog discovered on our first ride. I don't think she liked a 25-30 pound platform falling forward on her!

Bunk2 020.jpg (65950 bytes)To secure it I used a 6" ball bungee. I connected the aluminum back support and the platform through an eye. This works great. It keeps the platform from flipping forward, yet stretches enough that I don't have to mess with it during the setup of the bunk. My dog is much happier, thus Danielle is happier, which means I am happier!

The mattress is 4" foam. I wanted high density foam, but couldn't find it so we used regular foam. Four inches is thick enough - 6" would be too thick and would interfere with seating when the bunk is in the down position. The foam is comfortable, but high density would be an improvement if you can get it. Our foam is 71" x 30". We currently have it covered with a mattress cover until we can make a nicer cover from material of some sort.

The bunk worked out well. If I was to do it over again I'm not sure I would change much. The platform is way overbuilt and as a consequence is heavier than I  would like it. You could cut the framing by half and still have a very strong platform. I'd like to use high density foam, but if it proves to be a problem I can always add some memory foam, or switch it out.

Overall cost was around $99:  

  • Platform - $16 for 2 sheets underlayment, $4 for paint
  • Hardware - casters $5, pipe $5, flanges $4, aluminum $15, inserts and knobs $5
  • Mattress $42, cover $3

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Slide-N-Lock Cargo Tie Down System 

I wanted a tie-down system for carrying cargo on the deck of the tractor, but I did not like the looks or utility of the traditional D rings. I used the Slide-N-lock tie down system, which I bought at Arizona Trucks.  I paid $123.95, including shipping.


Slide-N-Lock's unique system allows you to position tie-downs right where you need them in seconds. Just pull the spring-loaded locking pin to slide the tie point smoothly and easily to the specific locating hole you want, attach your cargo and go. The Slide-N-Lock rails are made of high grade, T-6 Anodized Aluminum, and all locking pins and hardware are Stainless Steel for years of rust-free service. The capacity is 1,000lbs. per tie point in any direction.

The rails come as a set, and are available in 7", 22", 68", and 93". I used the 68" set, which come with 4 tie rings. I wanted an additional 2 rings, and discovered it was cheaper to order the 7" set of rails, which come with 2 rings, than to order the rings separately. The rails come as either natural aluminum (silver) or powder coated black. 

The rails mount via 1/4-20 stainless bolts every 10". In my application I had to tap the frame rail of the truck body  where I mounted them - since there was no access to the back of the bolts. I used black silicon caulk around the holes and on the bolt threads to keep water out of the bed rail (which is square tubing).




deckrail008web.jpg (23884 bytes)Here is what a rail looks like before installation. The rings are easy to put on/off and to locate to the right position.

deckrail003web.jpg (29296 bytes) Tapping the deck was pretty easy - the steel is fairly soft.

deckrail009web.jpg (50604 bytes) Here is a 68" rail installed.

deck_rail_boxtiedown1.jpg (71667 bytes) The 7" rails I bought just for the extra rings I put on the storage box between the fairings.





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Computer Workstation

Fuse cover 1_web.jpg (44895 bytes)WS 1.jpg (114193 bytes)  click on the images for a larger view

We use a GPS in combination with our laptop for navigation. We find we only use this when on long trips, or going into territory we have not been before, so generally the computer is not set up on the dash. But we needed a convenient way to view and secure the computer when it is in use. We looked at what others had done and came up with our solution. It works well for us, is simple to build, and gets rid of the CB holder (over the fuse cover) which we no longer needed, since we use a Cobra handheld CB (all functions are integrated in the CB "mike"). When the computer is not in use, it is easy to remove the slide portion, leaving just the fuse cover in place.

I first replaced the fuse cover with a 1/4" hardboard cover, painted to match the dash trim (black). Everything is sprayed with satin polyurethane. This fuse cover is always in place, but the rest of the computer slide is removable when not in use.

Computer slide closeup_web.jpg (36030 bytes)The slide and slide base is made of 1/4" hardboard. The base pivots on a small brass machine screw that goes into a threaded insert in the fuse cover (you can buy these inserts at Home stores). This allows either the passenger or driver to see the screen. The slide allows the computer to be pulled close to the navigator, for easier access to the keyboard and so those of us who are loosing our vision can focus on the screen well. The slide runs in 1/4" aluminum tracks available at the Home Center where they sell aluminum. Examine the pictures for construction details.

click on the images for a larger view

WS 4.jpg (110213 bytes)  WS 5.jpg (126202 bytes)  WS 6.jpg (123785 bytes)


Tablet Computer

In the picture above you can see a tablet computer on the dash in front of the passenger seat. This is held securely in place with Velcro. Nothing else is needed. This tablet is a Nexus 7 - with a 7" display. It is used to run Google Maps to supplement the navigation with Street Atlas on the Netbook. The combination is about perfect for naviagion. We also have Co Pilot on the tablet, if required. The tablet connects to the Internet via our private network, powered by an aircard. It can also run off my phone if the network goes down. It does require Internet connectivity for navigation, but this has not proven to be much of an issue. There is an in-built GPS. The tablet is powered via a 12-volt adaptor.

Some Hints

You need to put felt on the bottom of the slide base to keep from scratching up the fuse cover. The felt also helps the slide base to pivot smoothly over the screws that retain the fuse cover.

Second, the carriage bolt that the slide base swivels on needs to be recessed into the surface of the slide base. A large drill bit works fine. If you don't recess it, you will find that the head will restrict the movement of the slide forward and backward in the tracks.

To control the ease of movement forward/back of the slide, simply squeeze the aluminum track some. If you make it too loose, the slide will "walk" out of position as the truck moves.

Lastly, use Velcro to hold the computer in place.

Backup Cameras and Monitor

In my opinion, a big negative of everyday use of our Volvo 610 (or any sleeper) is restricted rear vision - especially in parking lots. Yes, you get used to using the mirrors and getting out and looking, etc. But stuff that is close is still in danger, no matter how careful you are. I find having a rear vision system convenient. As of August 2005 we have three cameras on our tractor. One on the back of the cab, one on the right mirror bar, and one directly behind the hitch.

The Cameras


Note: as of 2013 the best value for the $ that I can find on cameras and backup systems is on Ebay. Products sold by the seller 'leviathan_holdings' are high quality and work well. I have many, as do many other people, and we have had good luck with them.


I wanted a cheap system, but still effective. This meant assembling the pieces myself. The pre-packaged systems are great, but run upwards of $800 (as of 2010 you can find nice systems on Ebay for as little as $250). After researching it, I decided to buy a good monitor and a cheap camera. I thought this would suffice for my needs and it has turned out OK. I used an X10 Anaconda color wired camera as the primary camera on the back of the cab. Using a wireless camera is iffy, according to the people that have tried it - some work out - some don't. And since you have to supply 12-volt power to the camera you are running wires anyway. This X10 camera has 60-degree field of view. This is the minimum you need. I can see three lanes behind the tractor - one on each side of my lane. More field of view would be better, but this camera only cost $49 - which met my price goal. The image quality is acceptable for rear viewing of cars and other stuff, but marginal for hooking up. The issue is partly a function of the size of the monitor, in combination with the size of the lens on the camera, and the distance of the camera from the hitch - the hitch is a pretty small object as it appears on the monitor. I put white alignment stripes on my hitch plate and hitch head and this allows me to get real close to perfect alignment. A better quality camera would improve hookup tremendously, as would mounting the camera lower on the truck cab. The disadvantage of mounting the camera lower (say on the lowest grab bar) is that it is more difficult to route the wires invisibly. Everything is a tradeoff. The position I chose gives me good rear vision but is not optimal for hookup, but we pretty much do the hookup without the camera anyway.


To make hookup super-simple you could mount the camera on a stalk right behind the hitch. Several people who hookup without assistance have done this, and it works well. This does minimize your rear view, though. To solve this "quandary" we installed a third camera dedicated to hooking up. It is directly behind the hitch plate itself. This camera is a "Sam's Club" $39 color camera with IR capability. The image quality is about the same as the X-10's, as is the field of view. The real difference is that the Sam's camera is not weather resistant, so you have to build some sort of enclosure to protect it. I used PVC pipe.


My primary camera is mounted below the rear (little) window, resting on the horizontal rain gutter. The wire is run within the gutter, and down the gutter line along the vertical airfoil, then under the truck. It is not very noticeable, being nestled into the gutter line of the vertical foil, but you might want to paint the wire the color of your truck. The camera and wire is held onto the truck with white adhesive door/window caulk (good thing we have a white truck - if you have a colored truck, you might want to consider black caulk). It holds it fine. The camera comes with 60' of wire - more than enough. Everything (power/data) runs through one wire set, so hookup is simple. Check the X10 site for details - X10.


This camera is intended for use with home automation and security systems, so it uses 120-volt power reduced to 12 volts by an integral power brick. Just cut the brick off and wire the camera directly to an ignition-switched 12-volt power source in your fuse block. The camera uses minimal power, so don't worry about overloading whichever circuit you tap. I just found an unused fuse block that was ignition-switched and plugged in there. Make sure you maintain polarity - the white-striped wire is the positive feed. My ground is supplied from the back of the CB Radio power supply. The X10 wire code and pinouts is in a diagram at the bottom of this page. After using the camera for a year, I added a sun hood to it (the white cover in the picture, below). The camera would occasionally blank out, due to direct sun on the LCD. I used some PVC pipe and cut it to an appropriate size. It is held on with adhesive caulk.


The Monitor

I used a Mobile Authority M681 6.8" color monitor. This has reverse image and flip screen (horizontal/vertical). Also, a credit-card size remote control that allows direct access to the major functions. The quality and brightness (300 cd/m) is fine for application with the X10. Hooked to my sat system the image is much better...the camera is the limiting factor in this setup. However, I would not buy a monitor with less than 300 cd/m - monitors with up to 500 cd/m are available, but are significantly more expensive. The monitor also supports two video sources so you could attach a second camera and easily flip between them with the remote. There is a reverse-sense wire that would allow you to detect when reverse is engaged and flip to the video feed with the reverse camera automatically.  I did not use this. The monitor comes with a stand that is easy to mount on the vertical flat panel on the right portion of the drivers dash area. (the vertical fuse cover). This is the only area I found that allowed unrestricted view of the fender spot mirror by both my wife and myself. She is so much shorter than I am that mounting the monitor on the dash interfered with her view of the spot mirror. I thought of integrating the monitor into the door of the overhead storage bin above the driver, but it was too awkward to view there.

Total cost was - $49 camera, $196 for monitor (off of Ebay, including shipping/insurance). There were no extra costs, since the stand that came with the monitor was sufficient.


Future Additions


There is a blind region around 4-o'clock on the truck, because there are no windows on the passenger side of the sleeper. This makes it exciting to pull out of any intersection that Y's to your right. I do not have a powered passenger mirror, which would help minimize this problem. Because the monitor supports two video feeds I'm thinking about mounting a second camera on the passenger-side vertical foil angled out to the right of the truck. This would help with blind-side back-in campsites as well. Adding the second camera for $49 is a lot cheaper, and probably a superior solution, to adding a powered right mirror.


Update: after almost 2 years of living with limited vision to the dead area at 4 o'clock I installed a second camera. Joe Johnson gave me a "spare" X10 B&W camera (thanks Joe) and I mounted it on the mirror arm with "tacky-tack" (used to mount things in the RV). I'm a little concerned with impact from closing the door affecting the camera over the long-term. We will have to wait and see (update: the tacky-tack has held the camera in place for over 7 years with no issues). It works great when you need it,  especially for blind-side backing - no more guessing where you are when backing the trailer into those "backwards" campsites! Of course, if you have a powered mirror you can pretty much circumvent this problem that way.


I will probably paint the camera on the back of the cab white at some time - it will blend with the truck better this way.


After six years glare on the monitor has not been a problem, but shrouds are available that will help keep glare from the screen, or you can easily make your own. If this proves useful, I may add a shroud in the future. Positioning the monitor up on the dash would make it more subject to glare, and I think a shroud would be necessary.


Update 2013: after almost 10 years this camera is pretty worn out - UV has degraded the lens cover enough that  it is affecting the picture quality. Time for a replacement.


Managing Multiple Cameras


If you have a monitor that supports multiple video inputs then managing multiple cameras is not a problem, unless you want to have more than two cameras - the typical number of video sources monitors support. Since we now have three cameras I thought I would put in a switched system to feed the monitor, and circumvent the selector in the monitor itself.  


If you use X10 cameras, they only power up when they are "selected" by the base module. They take a little time to warm up, so ideally you want them all powered up and ready to use. The easiest way to do this is with a "selector box", which you will build yourself.


In order to do this you need to know the pin-outs on the cameras RJ-45 connector. The X-10 pinouts, left-to-right, as viewed from the end of the connector, with the tab on top is: 1 - ground, 2- video (yellow wire), 3 - ground, 4 - 12 volt (red wire), 5 - ground, 6 - audio (white wire) - see the diagram at the end of this page.


I built my selector box from a medium size plastic project box obtainable at Radio Shack. I used a 6-position rotary switch, also from Radio Shack. This switch requires you to solder the feed lines on, but it is a fairly simple process. To feed the camera outputs from the back of the truck to the dash I used category 5e Ethernet cable with connectors already on - 25' was more than enough. I ran this from the truck electrical panel mounted in the drivers compartment to the dash. Camera power is supplied by an ignition signal sent down the cat 5 cable on one of the lines from the fuse box at the dash to a relay. The relay controls power to the camera bank at the rear. The relay is used to simplify the wiring run from the cab - everything goes across the very light gauge cat5 cable. All cameras are "hot" when the ignition is on. This allows instant switching between cameras with no warm-up time.


At the project box on the dash the cat5 cable terminates in an RJ-45 jack mounted in the box. Within the project box the various camera inputs run to the appropriate switch position. A single output from the switch feeds the monitor. This way, the switch allows you to flip between camera views, while maintaining power on all cameras. It sounds complicated, but is really quite simple.  It is best if you solder the connectors onto the rotary switch.


At the driver compartment electrical center, where the rear camera inputs are centralized, I built a video jack board to plug the cameras into. The excess camera cable is tied to the frame under the truck.  You could easily cut this excess cable off, and just patch the raw wire ends to the cat5 cable. I used the plug board to make changes easy. To interface to the cat5 cable I cut the plug off and used a terminal strip to terminate all the ends. The plug board is wired directly to the terminal strip. This way I can move things around easily. You certainly would not have to do this complex of could simply wire-nut the appropriate camera ends to the cat5 cable.


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Sirius Satellite Radio


The stock Delco radio that was in our Volvo was not a very good radio, and it did not have a CD player, only a cassette player. We upgraded the radio to a Kenwood KDC-MP6025. It has an inbuilt Sirius display/controls with an external "brain" box (the satellite tuner). I chose Sirius over XM because the general consensus is that you get less drop outs with Sirius. This is because of the location of the Sirius satellites, and the fact that there are at least 2 satellites visible in any location vs. a single satellite with XM. The XM satellites are in geo synchronous orbit (like the DirecTV and Dish Network satellites). The Sirius satellites do figure 8's over the US. At least in theory, the Sirius satellites should provide better reception.

I looked at the external satellite radio receivers that can be moved from the truck to the trailer, or into another vehicle. I chose the integrated display (built into the radio) primarily because I have no need to move the receiver/display and I definitely don't need another box on my dash. It is getting crowded as is.

The radio is an upper line radio. It has 25 watts x 4 RMS of power, which makes a remarkable difference in the listening experience. I am definitely NOT an audiophile, so my requirements are not as strict as some. But the difference between the radios is both readily apparent, and huge. I thought I would have to upgrade the stock speakers, but this radio makes such a difference I probably will not do it. I may add an amp and subwoofer later and keep the existing speaker set. You can always use the extra bass. If I did this, I would leave the front speakers powered by the radio, and move the rear speakers to the amp.


The Sirius satellite tuner box went in the space right behind the cup holders - vertically. There is 20 feet of cable from the radio to the satellite tuner box, so you can locate it pretty much anywhere. The limiting factor in location was the amount of antenna coax supplied with the magnetic base antenna. There was just enough antenna wire to reach from the roof to the cup holder. Since the tuner does not generate heat, it is OK to mount it here. It is easily removed for servicing, or to move it to another vehicle if I sell the Volvo.

The antenna mounted on the passenger side visor brace (on an existing screw), on a piece of metal stock for horizontal magnetic mounting. It is important to maintain a horizontal position for the antenna. The tiny coax was run through the visor light trim piece towards the passenger side. I used white silicon caulk to secure it where required. It then runs downward behind the vertical windshield trim to the door hinge area where a piece of horizontal trim allows it to enter the door area without exposure. It proceeds through the rubber door trim and along the front of the dash. It is not visible. It enters the dash through the Eaton autoshift wire run, and then across to the fuse center (behind the cup holder) to the tuner box. The whole thing is neat, and took half an hour - start to finish. The radio went in just as easy.

Sirius Reception

Sirius reception is 100% so far - and I've been trying to beat it. There are no directional issues (truck facing certain directions) with the mounting location on the visor, and the truck roof, which rises steeply behind the visor, does not interfere with signal acquisition. The antenna is not visible from the ground. (One note on the visor mounting position - it worked well on a Volvo 610, with a mid-height roof. I'm not sure that it would work as well on a full-height truck because of the additional cab above the visor.) In areas where XM is known to lose signal (like 4th of July Pass in Idaho) I have no problems. I have also driven on densely treed two lane roads, where the trees are right up to the road edge. Again, no reception problems. Another thing I've noticed - in heavy rain there are no drop outs like with satellite TV. So I guess that the Sirius birds are helping me out.

I now know why people love satellite radio, although I never thought I would. But the sound quality is NOTICEABLY better than over the air music, even to a non-audiophile like me. So, I guess I'm a happy camper.

Here are the Volvo wire id's for the speakers:

490 - Radio/CD Radio Feed (Power)
491 - CD Radio Power Stud Feed
492 - Radio Battery Feed
497L+ - Door Speaker Left, Positive
497L- - Door Speaker Left, Negative
498LR+ - Rear Speaker, Left, Positive
498LR- - Rear Speaker, Left, Negative
498RR+ - Rear Speaker, Right, Positive
498RR- - Rear Speaker, Right, Negative
499LF+ - Front Speaker, Left, Positive
499LF- - Front Speaker, Left, Negative
499RF+ - Front Speaker, Right, Positive
499RF- - Front Speaker, Right, Negative
L+ - Lover Left Rear, Positive
L- - Lower Left Rear, Negative
R+ - Lower Right Rear, Negative
R- - Lower Right Rear, Negative
S1+ - Subwoofer Coil 1, Positive
S1- - Subwoofer Coil 1, Negative
S2+ - Subwoofer Coil 2, Positive
S2- - Subwoofer Coil 2, Negative

You may find that your rear speaker wires read 498LA, 498LB, 498RA and 498RB.

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Adding a Sink

We added a sink to our Volvo 610. Some 770/780's come with sinks in them, but the 600 series does not. There are various methods of adding them; the biggest issue is plumbing in the tanks and pump. The actual sink is the easy part. You can see our sink project - and some others - in our Picasa album.

Convenience Boxes

shifterbox.jpg (70879 bytes)We wanted a way to keep our FRS (2-way) radios handy. We use these all the time. We take them into Wal-Mart (that way we don't have to stay together), into the mall, around campgrounds, and of course, we use them when we are backing into our site (along with hand signals. Danielle does the campground registration, so she grabs one when she goes into the office, in case she has to ask me something.
We first tried to directly Velcro them to the side of the autoshift console. That "kind of" worked, but they kept falling off, or the Velcro kept coming off the back of the radio.
So, I built a little box to put them in. The box hangs from Velcro, and is sized to fit on the console without interfering with walking through. Our cell phone also fits into the box, although it is not shown. The entire thing works well.

The Hitch

broken frame 2.jpg (74701 bytes)After much research we decided to switch the commercial Holland hitch to a TrailerSaver air suspension hitch. The Holland hitch can be used with 5th wheel RVs if you weld a plate onto the dip in the hitch plate that is intended to hold grease (Fontain hitches should not need this modification). We had this done on our hitch just in case we needed to tow before upgrading to the air suspension hitch. We never used it, though. Wiring for the brake controller is described in the Trailer Light Converter section. This page concentrates on hitch selection and issues.


There are a number of people that tow with the commercial hitch, with no reported problems due to impact. Others who have towed with the commercial hitch have had fractured hitch heads and welds fractured on the trailer. If you do tow with the commercial hitch, you would want to be sure that you convert the tandem axles to single (lighter suspension). In the pictures above you can see the result of towing with a HDT and the commercial hitch (click on the second picture to expand it). Could it happen to you? Maybe not, but why take the chance? The hitch is not the place to save money, in our opinion.


We decided to convert to an air suspension hitch based on our observations of our Reese hitch on our F550. We are glad that we did it; watching the trailer float through rough roads confirms to us that there is an advantage to having the air hitch in addition to the existing air suspension on the tractor. Whether it is worth the expense is your own judgment. Since we intended to have a hauler bed built, leaving the commercial hitch on was not a viable alternative for us.


Hitch_trailairinterference.jpg (58770 bytes)There are a number of choices when selecting an air suspension hitch. You can go with a truck-mounted hitch, or use a hitch like the TrailAir that mounts to the hitch head of the trailer itself. We looked at the TrailAir carefully, both before and after acquiring the tractor. Our original intent was to use the TrailAir on our F550 and Reese hitch. This would have worked well with the fully articulating Reese hitch. However, use of the TrailAir with the tractor and the commercial Holland hitch is not the best solution, in our opinion, because the TrailAir does not provide full articulation - it is designed to be used in conjunction with a side-articulating conventional hitch like the Reese. While the TrailAir provides adequate vertical cushioning, the Holland hitch (and other commercial hitches) does not provide sideways movement - only fore and aft. I would be concerned with the lateral forces applied by the mass of the tractor, through the commercial hitch, to the TrailAir hitch head. You could avoid this issue by putting a conventional fully articulating hitch on the tractor, but you are probably going to run into hitch height problems unless you recess the hitch into the tractor frame rails. All this adds expense and aggravation - we found it easier to skip right to the air hitch. An additional issue with the TrailAir comes with its use on a truck with a hauler body on it. The TrailAir has a long and low plate to support its components. This plate extends rearward quite a bit, depending on the TrailAir model. It can interfere with a hauler body where the hitch is contained in a trough. If you are building a flatbed, this would not be an issue. You can see this in the picture above.


Within the class of truck mounted hitches there are many to choose from. At the time I built up the truck, the primary selection criterion for us was the hitch plate height. Many of the available hitches were too high for our trailer to ride level. These hitches are primarily designed for use with MDTs, which have a lower frame height, and thus a lower mounting height for the hitch. When applied to a class 8 tractor many of them end up being too high for the trailer to ride level. TrailerSaver has the lowest riding hitch we could find, thus our choice of TrailerSaver.  Since we installed the Trailersaver hitch we have discovered the Advanced Air Hitch It is also 10" high, and has a Binkley head, with air bag side cushioning, as well as fore-aft air bag cushioning. It also has a higher pin weight rating than the standard TrailerSaver. It is an interesting hitch and is worth a look if you are in the hitch market. It costs considerably more than a TrailerSaver, so we would not have used it, even if it was available at the time we chose our hitch.


If and when I build a new truck I will use what I consider the best hitch available on today's market - the ET Hitch. Nothing is built stronger, and it is designed to drop into the frame rails of the tractor. It has a steel bottom plate integrated into the design, so that saves you adding the steel plate. It is competitively priced and is simply the best hitch to use, in my opinion. A video describing the ET Sr. hitch is here.


hitch_plate.jpg (399719 bytes)Our truck has the frame cut 39" from the rear of the back tire. This allows for good-sized boxes behind the axle, and for enough deck space to carry toys. We removed the Holland hitch and the sliding mechanism. We bolted a 70" x 42" x ½" steel plate to the steel angle that originally supported the air-slide Holland hitch. This plate has three mounting locations for the hitch. The rearmost location places the kingpin 14" from the rear of the truck (39" behind the axle). The center location is 32" from the rear (23" behind the axle), and the most forward location is 44" from the rear (8" behind the center of the axle). Unlike pickup trucks, class 8 tractors can have the hitch mounted anywhere and perform properly. All the hitch manufacturers I discussed this with said we could mount it anywhere we wanted without problems.  We have been running with it in the middle position without any issues.  Remember, the further back the hitch is, the better the trailer tracks to the tractor, and the more deck space you have available for other uses.  In our case, with our short 182" wheelbase, in order to fit an ATV or motorcycle on the deck we will have to position the trailer in the middle or rear-most location. Your choice of hitch location is dictated primarily by your carrying requirements. If you don't want to carry anything on the deck, then you would probably close the gap between the tractor and trailer as much as possible.


Many people add extra weight in the form of a 1 inch steel deck that they mount the hitch on. This is a good idea if you can afford the sacrifice in final hitch head height. In our case, we decided that we could not afford the height increase.  Adding the extra weight would result in a better ride when bobtail, and slightly better braking performance. However, we found the ride fine with the 600 lbs added by the steel plate and the TrailerSaver hitch, even with our short wheelbase. 


While having the bed built we temporarily removed the steel plate and hitch. I did not think this would make much difference in the ride quality - boy was I wrong! It was like night and day - removing the 600 lbs RADICALLY changed the ride quality. You really do need that weight. Now that the body is on (to the tune of about 2000 lbs - with the hitch) the ride has improved even further.


Our final ride height on our first trailer we towed with the tractor (the Kountry Star), when hooked up with 75lbs. of air in the hitch, and with 3640lbs on the pin, was 20.5" from the tractors steel deck plate. The deck plate itself is 39 1/4" from the ground and it is 11" from the trailer hitch plate down to the tractor deck plate (this makes the hitch head about 50 1/4" from the ground).  On that trailer, the trailer hitch head was fully retracted.  Measuring the beltline of the trailer indicated a 1.5" drop from the front to the rear of the 36 foot trailer. This was not noticeable visually, and the trailer level indicated that the trailer was actually level so it was hard to tell if it was off any.  Note that TrailerSaver says that the hitch plate in its lowest location is 10" (from the mounting deck) but this is without the required air in the hitch, which added the extra inch. We were probably running a little more air than we need in the hitch - we could have gone down to 65 lbs or so and stayed within the guidelines of the hitch, but this does not lower the final height significantly.


Our next trailer, a Royals International, was lifted 3" by the previous owner, so there were no level issues. We did have to recess the trailer hitch head to it's next-to-last position in order to get level.  With the trailer pin weight slightly over 5,000 pounds we had to run about 95 psi in the hitch - which is too high for optimal cushioning.  You can add a third air bag to the hitch, which results in the ability to run reduced pressures - resulting in a softer ride for the trailer.  After about a year, we added this third air bag - mainly to increase the current 5000lb. pin weight rating (which we are at) to 7500 lbs.


When looking at hitches, measure carefully. Ride height is the single most critical measurement. You do have the option of dropping the hitch into the frame rails, but this will add cost. Also, be aware that if you do this, your rear air suspension dump may be limited by the amount you recess the hitch unless you relocate some of the air system components. You might also have to remove, or modify the cross-frame brace on a Volvo 610 - depending on where you locate the hitch. Assuming you bolt in a flat plate for the hitch, it probably would not matter if you remove the cross brace. If you drop the hitch between the rails, a good final hitch height to aim for is 46-47". This would accommodate almost all trailers, without raising them. If you want to see an example of a hitch mounted between the frame rails, look at Mark and Dale Bruss's website: They have quite a bit of good info on converting their Volvo 770.


When we build the next truck body we will drop the hitch between the rails, even though it will complicate things on the build. On Volvo's there is a cross member between the frame rails to the rear of (or near) the axle. There are a lot of air-system valves and components mounted on this cross-brace. Depending on where this is, and where you want your hitch location, you may need to cut this down or remove it. Some people move it more forward in order to have room for the hitch plate to drop between the frame rails. On a short wheelbase conversion like ours there is no room to move this brace forward without interfering with the ride level valve and other components. So on a short wb tractor where you want to recess the hitch, your only practical choice is to move the hitch far enough to the rear to avoid interfering with the cross-brace. Careful planning of the body is required to get this right. There is no problem moving the hitch 3-4' behind the axle center line.


If you are concerned about twisting forces flexing the frame then you might add a cross brace at the top of the frame members. The hitch plate will brace the bottom frame members. All frame shops I have discussed this modification with have approved this. Especially if you have a body on the truck there will be more than enough bracing provided.


Adding the Third Airbag
Because our pin weight on the Royals International ran slightly over 5000 lbs (depending on what was in the trailer and where) we decided it would be wise to add the optional 3rd air bag to the TrailerSaver hitch. This bag costs $300 - you can install it yourself. With the bag comes 2 bolts for the top mount, 2 self tapping screws for the bottom mount, a T for the airline, and about 12" of extra airline for the new bag. TrailerSaver says it takes about an hour to install. Maybe after you've done a few, but I would plan on 2 hours.
Installation instructions are on the TrailerSaver website. There are a couple of things to watch out for that they don't tell you about. First, check the air fitting that is already in the bottom of the third bag. You need to make sure it is tight, or you will be removing the bag later to fix the air leak (wonder how I know this?). Second, make sure you do not over tighten the 2 bolts in the top of the airbag, where they go through the swing arm. The holes tapped in the airbag top plate are very soft and can be stripped.
The entire thing is really pretty simple to do. The hardest part is drilling the 4 holes. You may only have to drill 2 holes, since newer hitches already have the swing arm holes drilled (for mounting the top of the airbag).

The pictures below tell the on them to expand.

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