M1083A1 or m923A2?

[Suprman]

Speed is limited by gearing and engine rpm limited at 2600 rpms. The u joints are inexpensive over the counter. I had a parts truck I took the driveshafts off for one and I am going to have the old ones rebuild for the second truck. It was just the slip joints that had play. 3126 is computer controlled I would think mileage is pretty well maximised.

 

[Duckworthe]

My M1078 gets a happy 8.5 mpg on a great day. Last trip from San Diego to Las Vegas and back was around 7mpg. They are big and flat nosed and are heavy pushing huge tires. I don't think you will ever get more than 9.5 mpg out of FMTV. If someone out there has do this, please let me know. The exhaust really isn't all that restrictive like cars are today. The military doesn't really have to worry about all the smog rules as they are building for power. Just listen to a military cargo aircraft compared to a civilian cargo aircraft. However, the FMTV trucks do meet the EPA's requirements and have the sticker on the valve cover to back it up. I agree that it is smiles per mile. These truck are neck breakers when you drive them. By that I mean, everyone does triple takes at them! I can tell you that LMTV's are a very smooth ride. Some put air ride seat in them but I don't see why as mine rides so very smooth that it seems unnecessary. I just installed some aftermarket seats. Anyway, good luck on your decision making. View attachment 652495

No I don't have a build site or web site. I just build and share as people need. I've had people from Oregon, Montana and other places fly into San Diego to look at it and I usually spend about 7-8 hours with them talking about the pros and cons. I let them drive it so they can feel how it drives. I take them on and off road so they know what it can do. I will tell you, I wheel this thing! I take it through some rough stuff. Not just through the gravel. I go through the same rock crawling trails as the jeeps and all do, as long as I can fit! the only thing I haven't driven through is deep mud. just don't have that type of terrain here. LOL call me if you want. 619-952-4337.
Eric

 

[DiverDarrell]

The cat 3116, 3126, and c7 though are called throwaway engines can be rebuilt like every other non sleeved engine. Cat did make a v8 diesel that was junk but this inline 6 series engine has been a good performer. It was meant to be run at a little higher rpm and should see best mpg in the 1800-2200 rpm range. The 3116 has some easy performance upgrades which will also help mpg. For one adjusting the fuel rack, with the addition of a slightly larger turbo to help with the added heat. Then for more money the injectors. The military used the 3116 in a 350hp config in the Stryker platforms, so a 100 hp can be added. My opinion is that in the Lmtv 225hp was an under powered engine for the weight and expectations of the trucks. They should have got the 275hp of the 1083 series trucks. As suprman can attest the 330hp engine is a whole better beast. 7.2l vs 6.6l. Since I have the 3116 my end goal will be 300hp, with high speed gears should be Turing 2000 rpm at 60mph, and a guestamation of 10+mpg. Also assuming ctis disconnected running max psi in the tires that still pass the chalk test.

 

[ramdough]

So you are not tuning up all of the way to 350? Is that for reliability?

Would your recommendation be to get the 3126 or the 3116 then?


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[ramdough]

Thanks to everyone on this thread, after much discussion, help from everyone, and some research, I have decided on a 108x chassis. Probably the 1088, but I will have to see what is at auction when I am ready to pull the trigger.

Thanks to everyone!


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[MGKMartin]

The 1088A1's tend to be about 1/3 the price of a 1083A1 since everyone wants the cargo version. The frame is a little bit shorter (~8" or so), doesn't have the bed subframe of the 1083, and has the trans cooler vertical behind the cab instead of between the frame rails. The pintle mount plate, sway-bar mounts, and tail light assemblies are also different. If you are going to build an overland camper anyway, you can get the 1083 trans cooler from someone parting a truck out and use c-channel for the added subframe for your camper build. The only slightly tricky thing is the sway-bar mounts and the tail lights since they shortened the frame and the tail lights mount where the sway-bar mount normally goes. Probably the easiest thing is to get sway-bar mounts from a truck that is being parted out and mount the lights under the camper box. Since I am turning my 1088A1 into a 1083A1P2, I am extending my frame rails and will mount everything in the original position.

Here are pictures of the back of a 1088a1 with the 5th wheel removed and a 1083a1 in the process of being stripped for parts for the 1983a1p2 build. Shock mount to back of frame rail is 8" longer on the 1083a1.

 

[scottmandu]

I am guessing that the view from the FMTV of the ground in front is better, better door seals, better wipers, more space..... probably easier to soundproof the cab (fewer air leak paths, easier to add matts than seal leaky seals). I am assuming I could make it more comfortable for 6-10 hour drives.

My biggest concern right now is reliability and parts availability. I really don't want to break down and not have parts. Also, I will be working on it myself. I don't mind fixing something that is broken, I just don't want to have to fix something every time I drive it.
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Cat has had all the engine parts that I have needed which hasn't been an extensive list, just filters, and a few gaskets and seals. Allison also has had in stock the trans parts I needed (filters, a couple of o-rings, a hose and a sensor). If you need something specific to the LMTV is can be hard to find but even with numbers of truck out there are small , the supply of parts is good, either through surplus vendors or through flea bay.

 

[ramdough]

Martin, can you take some pictures of the frame top down and a few side shots so I can see the placement of everything around the frame? Also, maybe some close ups of the back of the cab? I would like to see what I have to work with.


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[MGKMartin]

 

[ramdough]

After looking at your truck, I think I can leave the truck suspension alone and move the tail lights to my box. Those pictures are incredibly helpful. Thank you. It almost looks like the top of the hydraulics control panel is almost even with the cab floor under the passenger seat. Is that a true statement?

I am thinking of removing the tire carrier and making a crawl through space. Just checking relative heights.


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[MGKMartin]

yes, I think it is within an inch or so. I can check tomorrow when it is light.

For the crawl space, keep in mind that this is a cab-over. You need to make sure you can still easily tilt the cab to access the engine.

 

[Suprman]

I think you can relocate the hyd control panel if you wanted. You would have to custom make some line extensions.

 

[ramdough]

I planned to either have a clamp on bellows ring for the cab, or possible some rare earth magnets to hold the bellows in place. Either way I will make it disconnect and have a rain cover when disconnected.


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[ramdough]

If the hydraulic controls were moved and the tire carrier gone, how close would the first big thing on the left side be to the centerline? Not sure if that makes sense.


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[ramdough]

I was hoping to not have to move the air cleaner or fluid fills.


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[MGKMartin]

Agreed. There isn't much play in the lines and it is right up against the top of the tank in the 1088's so it can't go down any, but with some line extensions or new lines, I don't see a problem moving it. However, it shouldn't be in the way for a pass-through. You would probably need to move the hydro-pneumatic pump and tank though so you could have the pass-through in the center instead of where the passenger seat is. It is doable, but looks like it would be a lot of work to make a pass-through workable.

 

[MGKMartin]

Tire carrier goes almost exactly to the center line on the passenger side. The very next thing is the hydro-pneumatic pump and tank for raising and lowering the cab, spare tire carrier, and suspension compression. If you wanted to make it a crawl-through tunnel, you could probably build a floor over the top of the tank. You just need to make sure you can still access the fill port on top.

 

[Suprman]

I have wanted to add a back window to my cargo truck. The cab has an indent where a window would be. I think you could make a rear boot system out of tent/top material and use snaps and Velcro to make a reasonably waterproof seal. I have an extra rear cab section you could make a cab and a half.

 

[ramdough]

I have wanted to add a back window to my cargo truck. The cab has an indent where a window would be. I think you could make a rear boot system out of tent/top material and use snaps and Velcro to make a reasonably waterproof seal. I have an extra rear cab section you could make a cab and a half.

Yeah, it may become a crawl space and not a big hole so I move less truck stuff.

It might be nice to add windows on the edge indents as well.

Don't tempt me on the cab and a half


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[ramdough]

Tire carrier goes almost exactly to the center line on the passenger side. The very next thing is the hydro-pneumatic pump and tank for raising and lowering the cab, spare tire carrier, and suspension compression. If you wanted to make it a crawl-through tunnel, you could probably build a floor over the top of the tank. You just need to make sure you can still access the fill port on top.

View attachment 652712

Any idea how high that is above the highest drive train component? Looks like the transfer case or transmission protrudes above the frame rails.


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