MDT Conversion - Thinking It Through

[Filthy]

I'm considering a MDT conversion to an RV, and I'm trying to understand the trade-offs of some choices, and maybe figure out what I can do and what I should hand off to a fabricator.

Who: me. I'm middle-age, grew up on a farm, live in the city now, have degrees in Electrical Engineering and in Physics. I know my way around SolidWorks and some other CAD programs, if needed. I used to work on cars, but my project car is on hold until after the pandemic. I can weld a functional bead without setting myself on fire.

Where: I'm in PHX

When: I figure it will take at least 2 years to be 'finished', probably 18 months to be rolling down the road and camping.

Why: no one makes what I want - a double/crew cab SuperC on an MDT frame, <30' OAL, no slide-outs. I have 3 little kids, and I don't feel comfortable with them riding in the house of my Tioga 26Q. That vehicle just isn't set up to roll down the road with children. No slides for safety, reliability, weight reasons. Short length because my wife might need to drive it, and we just don't think we'll outgrow a ~26' house in the next 10 years.

What: a conversion of an double/crew cab MDT. Source vehicle and configuration is where I'm hoping someone can help.
Is there a 'best source truck?
I'm trying to get 2009 or older, or newer than 2015. I understand the new diesel engines weren't the best when they first rolled out. I think the newer ones are quieter, but I also have some experience with soundproofing.
Where should the rear-axle be located? centered under the load? or as far back as the suspension will allow? what are the trade-offs in axle location? I don't think it's a big deal to move the rear axle (measure, drill, weld), but correct me if I'm wrong.

Right now I'm looking at older moving trucks, or but my ideal would be (I think) an ambulance. I think it would have the lower ride height and better handling/cruising.

Anyway, I have lots of other questions - and I've read the first few pages of posts in this and the "general" forum, so hopefully I'm not asking something that's been asked a thousand times before...but probably.

[Filthy]

one more question:

what's the best source for the internal systems of the house? I was looking at salvage Class Cs, but then I thought maybe a Class A would be built on a more similar chassis (freightliner, for example) and the systems would swap over with less hassle.

or maybe a 5th wheel or travel trailer has all the right systems at a better price...thoughts?

[cagebob1]

I have a friend who has a truck that might fit your needs. It's a 2003 Freightliner FL80 crew cab. It's a low mileage( relatively ), rust free truck with Cat power. If you are interested, let me know and I'll put you in touch with him.

[6cuda6]

Ill add more later but one thing is if your going automatic make sure it has an Allison....its probably the most reliable choice.

[6cuda6]

My suggestion, first and foremost, is to ask yourself what kind of camping are you thinking of doing as most Parks in the US go by the 10 foot rule, so every 10 feet moves you into specific camping spots so a 30 foot spot might perhaps be sided on 3 sides with trees but a 40 plus foot spot will just be a drive through alley way. Also think of were you going, as an example some of the mountain passes in some of the parks are restricted to "X" feet.....ill kinda call that step one.

Step 2: Is to figure out what your local licensing laws are, so here were i live most MDT's without air brakes dont need an airbrake endorsement to drive them but one that has air brakes does [here thats 1000$ to add to mine and my wifes license].

Step 3: Next make sure you know what you need to convert it from commercial to RV or passenger vehicle status.

Step 4: Next figure out the necessities you want then look for something that suits your "box"......you have already figured out that you want something you can put the family in the cab......next i would figure out how much fluid your going to want on board....fluid is really heavy and that will dictate axle placement [ie: 150 gallons of water 6 feet off the rear axle is not the best]. Gray tank, black tank, generator, batteries and such all take up real estate that you may want for storage....so think it over carefully and then lay everything out in a drawing, even if that drawing is a rough sketch on graph paper.

Stretching a frame, as its known, although simple in theory is a very difficult thing to do safely and correctly [i can fab, weld etc but will have a certified welder do mine] and adds to your build cost...and dont forget that it cost the same to stretch the frame 4 inches as it does 4 feet.....lol.....so if you know going in how long a frame you need and find something already built around that "box" dimension your money ahead.

As for what year? Well anything before 2010 will not have a DEF/SCR emission system on it and anything before 2007 will not have any emission system at all......so for me, being a mechanic i stayed away from anything post 2010 as fixing emission stuff is major money. I currently am working with a 2008 so it has a DPF but no DEF, it was a compromise for what i wanted and needed but if i was going MDT it would be a none emission truck...period.

I'm sure others can add more insight into this as the above is just my opinion and the discussions my wife and I are having or have had getting everything ready to embark on our build as well....

[LargeMarge]

Our rig -- 1997 Ford CF8000 commercial truck we converted to our concept of an ExpeditionVehicle.
Cummins 8.3 mechanical, Allison 3060, air-locker axle.
Our situation -- full-time live-aboard, boondock exclusively.
Remote forests, winters on Baja beaches.
Twenty-four months twenty-four thousand miles around south America.
Alaska, Panama, all over north and central America.

*****

2003, my Very Significant Other got sick.
We quickly wrote our Requirements Statement.
Essentials include:
* common off-the-shelf (COTS) components.
* compatible with Third World fuels and repair capabilities.
* ground clearance so we can avoid hang-ups on boulders and stumps
* a 'million-mile' commercial chassis
* cheap enough to abandon.

Naturally, we acquired a commercial truck for exploring.
Our conversion took less than a week... while selling everything.
Less than a week after getting the diagnosis, we left Oregon with the vague goal of 'south!'.

Instead of fussing with computers to fit our needs into the available interior, we built cardboard-box mock-ups to represent cabinets, counters, furniture.
By changing their shapes and sizes, we arranged these for access, utility, traffic.

After we established our interior design, we placed mock-up windows so we could see outside.
We have 3x1 dual-pane stand-still house windows centered at our eye-level while standing inside.
This puts the windows about eight-feet above ground level.
Unless peepers are up-hill or on a structure, nobody can see in.

My peeve with factory RecreationVehicles is yuge picture windows.
With increasing jealousy from the slackers, I imagine a big window on a fancy rig could be a tempting target.

My suggestion:
* avoid believing 'this rig is our forever rig'.

After nearly two decades of full-time live-aboard, our rig is constantly evolving.
With our modular interior, we can modify at-will... or empty it to return to commercial use.

Another suggestion:
* shrink your needs.
Quit them tuba lessons, take up harmonica.

Our interior is seven paces long, three paces across.
Our GVWR is 29,000#, our weight across the scales is 14,000#... giving a nice cushion for cargo.
Compared to a Sprinter van or other factory RecreationVehicle, that would be more now, wouldn't it.

*****

I have experience with educated degreed individuals with exceptional abilities to consider stuff from every angle.
I also know van-dwellers in the getting-ready-to-start to build state.

If your Requirements Statement goals include 'hitting the road':
* Might you be over-thinking this?

[florida panhandler]

Yep, I have to agree with LargeMarge. Are you overthinking this?

You are young with a young family. I understand your concerns with safety for the kids, but you have to also realize that they are a heck of a lot more flexible to situations than you and your missus are.

My first class A was a 31' Georgia Boy class A on a Dodge 440 (OK, we won't talk about the *#^@) Dodge). We had 4 teenagers and we all slept comfortably. Lord, were they designed so much better back then?

A U-Dinette in the rear slept three easily in their sleeping bags, with the youngest daughter taking over the cabover pull down. Wife and I slept on a very comfortable Flexsteel couch. We had two barrel chairs opposite with seat belts, couch had seat belts, cab had a single driver's seat and a double wide passenger seat with two belts that rotated to the coach.

We slooooooowly decided just what did we actually need. It was another 3-4 years before we stepped up. Then the kids graduated and we stepped back until we finally, in our elder years, got into a class A that satisfied our needs. The kids got their own RV's and we group up now and then. Just some thoughts for you to hash over.

[Santa]

I welded on to the back so that there would only be one weld and then moved to rear wheels back. Go for it, it is your dream don't let the dream killers win.

[6cuda6]

Yup...dont get me wrong...i'm totally with Santa here.....as i said "think it and build it" but dont "think it to hard".

[Filthy]

Originally Posted by florida panhandler

Yep, I have to agree with LargeMarge. Are you overthinking this?

You are young with a young family. I understand your concerns with safety for the kids, but you have to also realize that they are a heck of a lot more flexible to situations than you and your missus are.

My first class A was a 31' Georgia Boy class A on a Dodge 440 (OK, we won't talk about the *#^@) Dodge). We had 4 teenagers and we all slept comfortably. Lord, were they designed so much better back then?

A U-Dinette in the rear slept three easily in their sleeping bags, with the youngest daughter taking over the cabover pull down. Wife and I slept on a very comfortable Flexsteel couch. We had two barrel chairs opposite with seat belts, couch had seat belts, cab had a single driver's seat and a double wide passenger seat with two belts that rotated to the coach.

We slooooooowly decided just what did we actually need. It was another 3-4 years before we stepped up. Then the kids graduated and we stepped back until we finally, in our elder years, got into a class A that satisfied our needs. The kids got their own RV's and we group up now and then. Just some thoughts for you to hash over.

appreciate ALL the responses, but I'll just quote this sentiment and try to answer it all.


The short answer is I'm just thinking about it, and I like to think about stuff because I'm an engineer. It will be at least a year, probably a little longer, until I actually start on a custom conversion. I don't think it will be a "forever" RV, but I want a plan that's scalable and modular so it keeps enough flexibility to adapt to our changing lifestyle/family. I expect that we'll spend a lot more time on the road as the kids get older, and if it works out like that we'll want a vehicle that's safer rolling down the highway, without compromising the way we use it.

I checked with registering a custom conversion in AZ, not difficult, but AZ registration is expensive. But to change an MDT to an RV it needs to be open between the cab and the house, and pass an inspection. If it's Class 6, I won't need a CDL or air brake endorsement. If I need a CDL, I can get an exemption 'endorsement' if I do the skills test in a vehicle without air brakes.

The idea is that if the time comes to buy a truck, I'll be an informed buyer and know a good deal when it's available.