Best 5-Ton Chassis for Expedition Truck with Classic Cabover Body?

[Marbleman60]

I am interested in buying a military 5 ton tandem rear axle truck to remove the cab and install a 1950's GMC Cannonball COE Semi cab and sleeper on top, with a M35A2C drop side 12' bed or similar. Above is a mock up I did and an AI rendering. The Cannonball is a non-tilt-cab COE semi. The cab is rather spacious with a removable floor for working on the engine. They originally accommodated up to a 6-71 detroit. There also also small hoods on either side of the grill that open for access to the front of the motor. The cab floor is above the top of the front fenders. I understand all of these chassis will require custom steering setups and cab mounts, among other things. Air brakes are fine. I want to run super singles, such as 14R20, 16R20, or 395's. It will be what you might hear referred to as an "expedition truck".

I was thinking an M1083/M1088 MTV could be the best chassis for this given the power and top speed with "eco hubs" that remove the 2:1 hub reduction gears, but I am worried about long term availability of the electronic components for the engine/trans on those trucks.

CTIS would be a great perk to have, but might not be worth the hassle. It seems relatively easy to keep going on the MTV's. The truck needs to cruise comfortably at 60+ MPH and ideally be able to hit 70+ for occasional passing. I do not want the exhaust to be deafening, and want as smooth of a ride as possible (taking into consideration its a 25,000+ lb truck). Parts availability and ease of finding service centers capable of emergency repairs when on road trips cross-country is very important, but I am willing to carry some spare parts and do most of my own work when at home.

I plan to do some overlanding with the truck, whenever I can find trails it will fit down. This will often require long highway trips to get to overlanding locations, followed by days of off-roading. I would normally just be hauling camping gear but may put a shelter on the back at some point or build a shelter container. Otherwise I plan to move a couple pallets of building supplies or car parts at any given time, not approaching the 5 ton rating.

Any suggestions for what chassis to start with? It seems the M1088A1 and M931A2 are the leading options from my research.

 

[dwlindsey]

I've been working on an M1088, getting it ready for a habitat box.

You can see what I have in mind, here:
https://www.steelsoldiers.com/threads/little-bear-build.223420/

It seems to me that changing the cab as you propose is a very large project and I won'der why you would take that on. There are an astonishing number of air lines, air valves and electrical connections. Getting the chassis to work correctly after changing the cab would be, I think, a really big project.

With a some effort the FMTV cab can become quite acceptable.

It will be 6 to 12 months before I start putting the habitat box on, but so far I'm a big fan of this chassis.

Eco hubs are installed and in my opinion are essential

 

[Marbleman60]

It seems to me that changing the cab as you propose is a very large project and I won'der why you would take that on. There are an astonishing number of air lines, air valves and electrical connections. Getting the chassis to work correctly after changing the cab would be, I think, a really big project.

It would absolutely be a very serious undertaking, but I want a Cannonball and would be chassis swapping it no matter what. The cab has to be fully gutted for frame-off restoration anyways. It's a very common practice with these old semi tractors since they ride like bricks and have extremely little articulation, plus chassis/brake parts are getting extremely hard to find. I'm also not interested in running a Detroit 2-stroke diesel or huge gas engine like they all came with.

People often put them on old U-Haul truck, bus, or motor home chassis but I want something with more grunt and capability. I'm an electrical engineer in the automotive and defense harness industry, and I have some mechanical engineering background, so I'm not concerned about the difficulty of the swap, especially if I eliminate the (FMTV) hydraulic system entirely, since the cab doesn't tilt and the spare tire could be lowered with a small winch.

I also want to tag it as a 50's GMC (kosher in my state) which grants me antique plates, non-commercial insurance, no CDL related weight restrictions within reason when hauling my own gear (ex. 50k+ GCW would be fine with a standard license on antique plates), and I would have lifetime registration with no annual inspections required.

 

[dwlindsey]

That's a very big but cool project. I'd love to see it when you are done.

There's one M1083 for sale on Govplanet right now. It's in Wisconsin and is owned by a private seller. "Buy it Now" price of $25,000. It's an A0 truck with a 3116 CAT. That is all mechanical. My preference is for an A1 or later truck with a 3125 or C7 . Mine is an A1 with a 3126 engine.

There are no M1088s for sale on GovPlanet right now, but they do come up and can usually be had for less than $10,000.

 

[Marbleman60]

That's a very big but cool project. I'd love to see it when you are done.

There's one M1083 for sale on Govplanet right now. It's in Wisconsin and is owned by a private seller. "Buy it Now" price of $25,000. It's an A0 truck with a 3116 CAT. That is all mechanical. My preference is for an A1 or later truck with a 3125 or C7 . Mine is an A1 with a 3126 engine.

There are no M1088s for sale on GovPlanet right now, but they do come up and can usually be had for less than $10,000.

It definitely seems like a M1088 would be the way to go for an MTV given the heavier rear suspension and lower purchase price. The heavy suspension would be good to have if I put a 6000+ lb camper skid in the back.

I've been looking into doing cab air-ride like the MTV has stock and it seems quite simple to add to a semi-style cab.