Looking to Upgrade to HDT

So Your Are Looking to Upgrade to an HDT


For those who are thinking about moving up to an HDT (Heavy Duty Truck) you might be interested in knowing a little bit about the driving experience and work backgrounds of some of those who have chosen to purchase an HDT to pull their 5th-wheel trailers after owning other classes of trucks which we felt were not suited to safely pull larger 5th-Wheels primarily due to lack of power and the braking ability that the class 3-6 trucks offer.

Contrary to some beliefs, you do not need any prior background in driving an HDT to safely operate one as long as you Familiarize yourself with the workings of the trucks as they basically have the same footprint and options available on your every day run-of-the-mill Dually Pickup except for the overall height of an HDT, air ride seats and air brakes.

Why is an HDT the Better Choice for our Application?

Some of the best HDT introduction information will be found on Mark & Dale Bruss' (Mark) Why a Big Truck and Jack Mayer (Jack)'s (Jack) Choosing Betwwen an MDT and HDT both cover the subjects on the concepts of why to consider an HDT.

And for the Women Whose Better Halves Have the Urge to Purchase a New Toy:

1. RDBE (for those in the know) -aka- Rigs Driven by Estrogen

Federal Motor Home Guidelines:

Motor Home means a multi-purpose vehicle with motive power that is designed to provide temporary residential accommodations, as evidenced by the presence of at least four of the following facilities:

1. Cooking - A small microwave is generally acceptable.
2. Refrigeration or Ice Box - Either 110 Volt, 12 Volt or LP powered refrigerator is acceptable.
3. Self-contained Toilet - In most states a Porta Potty is acceptable.
4. Heating or Air Conditioning - Factory air/heat is acceptable w/separate sleeper berth control.
5. Potable Water Supply System including a Faucet and Sink.
6. Separate 110V Power Supply or LP Gas - A generator, inverter or shore power inlet is acceptable.

The above items are the Federal Guidelines and as such do not totaly define state rules for whether HDT's can be licensed as motor homes.  Every state has their own guidelines as to what does or does not qualify as a motor home therefore your state may or may not abide by the Federal Motor Home guidelines .  Many states use some part of the Federal Guidelines to qualify our HDT's as Motor Home conversions.

Many states do allow the classification of a converted HDT as a motor home as it is a simple way to license the vehicle as private and non-commercial.

The  FMVSS49CFR571.3Definitions.pdf


The Federal Motor Home Guidelines are located midways down the page in the Link above under the heading - [Editor's Note: Definition of " motor home " will be revised effective June 2, 2008.] that is highlighted in bold print.


Having a printed copy of the Federal Motor Home Guidelines with you may be beneficial when you try to register your HDT as a Motor Home in your state of residency, but remember, the state codes/regulations are the final decision.

Which Class 7 or Class 8 Tractor Would Serve Me Best?

If your looking for a specific make and model truck and need some questions answered that you cannot locate after using the Search Function free to PM a forum member or two who own that particular truck and we are sure they will be more than happy to answer your questions as best they can.


Based on the majority of trucks members have purchased for conversions the following three HDT's are the most popular for RV use.

Listed In Order Of Popularity:

1. The Volvo VNL610

With a 56" set-back front axle, 50 degree wheel cut, removable upper fairing, 61" sleeper area and optional Upper Bunk and relatively short wheelbase.

The 610 is the leader in popularity amongst most forum members due to it's relatively short wheelbase and mid height sleeper which is still high enough for most people to walk around without having to stoop over when they walk from one section of the cab to the other.

If your HDT is also going to be your daily driver when your on the road you also have the added advantage of a shorter cab height in comparison to a condo height cab when your in areas with a lot of low hanging tree limbs, telephone and cable TV lines or even power lines.

2. The Volvo VNL770

With a 56" set-back front axle, 50 degree wheel cut, 77" sleeper area with a fold up upper bunk that measures in at 40" wide by approximately 7' long with windows on either side of the bunk, a large abundance of interior storage space, in most cases a factory installed Work Station seating area that converts into a spacious 42" wide by 6.5' long bunk plus standard large functional screened windows in the lower sleeper area.

The majority of 770's also come with a bar height refrigerator "powered by 12 Volts alone or as a 12 Volt/110 Volt combination" installed in the cabinet directly behind the drivers seat and a few even include a small OEM stainless steel sink with a 12 Volt faucet that is mounted in the drawer directly above the refrigerator.  The sink option also includes small fresh water and gray water holding tanks that are installed in the outside drivers side storage compartment.


3. The Kenworth T-2000

With a 50" set-back front axle, 45 degree wheel cut, removable upper fairing, 75" sleeper area, above average storage space and optional lower sleeper berth windows. - BTW, if your looking to remove the upper fairing on a T-2000 Kenworth makes a stainless steel bolt kit with the proper seals to plug all the holes where the fairing attaches to the roof.

Like the Volvo 610, the T-2000 is very popular because the upper fairing is removable which gives you a Cab Height of approximately 11' 6" with the upper fairing removed as compared to 10'10" for a 610 with the upper fairing removed. Though not shown in the picture at approximately 13' 3" tall the Volvo 660/770 & condo height Peterbilt 387's are approximately the same height as a T-2000 with the upper fairing in place.

One drawback to the T-2000 is that it's more labor intensive to single one out therefore unless your planning to keep the tandem axle setup that's something to take into consideration before purchasing a T-2000.


Other More Popular Models:

1. The Volvo VNL660

With a 56" set-back front axle, 50 degree wheel cut, 61" condo height sleeper area with a factory installed Upper Bunk plus the factory installed Work Station seating area that many 660's were manufactured with along with the relatively short wheelbase of a 610.

The drawback that many see in the 660 is the condo height cab with only a 61" sleeper area.  Since the 660 and 770 are both 13' 3" tall ,quite a few people think the 770 with an additional 16" of living space is the better option if you need or want a condo height cab plus the sleeper area in the 660 is approximately 7" narrower than that of a 770.


2. The Volvo VNL42T/420

The VNL42T is a viable option if your not overly concerned about floor space, sleeper size and the creature comforts that comes with a larger cab.



The primary reason Volvo's are in demand for our application is the ease of singling out a Volvo, the quieter than normal cab, the 56" set back front axle and the 50 degree wheel cut which allows for a tighter than normal turning radius among any other HDT that is currently on the market. 

3. The Condo-Height and Mid-Height Peterbilt 387's

In time, Peterbilt 387s will surely become more popular as more AutoShift & Fully Automated Transmissions become available in the price range that most are willing to pay for a used HDT for RV use.

The Peterbilt has a set-back axle and 50 degree wheel-cut.



Jack Mayer (Jack) has a good write up on his web site,  Selecting Your Heavy Duty Truck about choosing between the various makes and models of HDT's.

If you've finally decided on a Volvo but aren't quite sure which model would serve you best, a mid-height 42T, 420, 610 or the condo height 770 and 660 then you might want to read Mark & Dale Bruss's (Mark) Why a Volvo Truck. and Why a Volvo 770 on why he chose to go with a Volvo 770

For more Information on the Volvo Model Line

For more Information on the Kenworth Model Line

For more Information on the Peterbilt Model Line

For more Information on the Freightliner Model Line