LMTV or?...

[justin22885]

So here is my situation. I am looking to buy land that does not have road access and build a homestead. This means I will need a vehicle that can both go offroad, and carry a good bit of supplies and equipment. The areas I am considering doing this is eastern WA state, Idaho, or more likely Alaska. This means something that can deal with a lot of snow and cold.

I was looking at the M35s, 5 tons, and LMTVs and the LMTV interests me before for a few reasons. It is a shorter vehicle, but it has the same size bed and carrying capacity as a full size unbobbed deuce. Something else that seems to be true for the LMTV is that the cab is also better sealed up which might be better for cold weather and heating, and the auto transmission is nice.

I would probably be making some modifications and upgrades as I go to better tailor it to my needs. I may look into suspension modifications to improve more regular off-road trail usage. I may look into proving its cold weather capabilities with insulation and heat, and cold-weather starting. And the consensus I am seeing is that people like the Allison transmission but hate the 3116 engine due to reliability issues and availability. Being in the middle of nowhere, reliability and availability of parts will be important so I may get the LMTV with the plan to replace the engine later on down the road, though what I have not yet decided what I would switch it to.

So, is the LMTV the type of vehicle I want? Or do you think I would be better off with one of the 6x6 vehicles available? If so, why?

 

[big block 88]

M939 series 5 ton is tye way to go. You can get a frankencab A2 and have a very tightly sealed cab.

I hate fmtv nothing but a disaster in iraq for us. I will never trust them.

 

[mkcoen]

If you don't mind getting a Class B or higher license then go with the 923. If you would prefer something that doesn't require additional government involvement go with the LMTV. I've had both and enjoyed driving both. There's positives and negatives to be had with either. Remember that military mechanics are trained to diagnose what isn't working and replace it versus diagnosing and repairing. Not trying to disparage anyone but that's the way the military is. There are a lot of things that go wrong with the LMTV that are repairable that wind up getting a truck deadlined and sold at auction instead of repaired. I've had both the LMTV and 923 break down and leave me sitting on the road so don't think one will and one won't.

 

[Karl kostman]

Good question Justin, as things sit the 939 series 5 ton is a tried and very true solution for a lot of applications. One thing that your going to need NO MATTER WHAT TRUCK you choose is a block heater on the truck engine and a place to plug them into. I am not that familiar with the starting characteristics with the FMTV series but with the 939 series pretty much anything under freezing your going to want it plugged in for at least a couple hours prior to starting.
Good Luck
Karl

 

[snowtrac nome]

Well here we go again I live in Nome AK I have a lmtv set up as a service truck it has worked nice for me the cab is roomy and sealed up nice. The 3116 is quite reliable as long as you have a tight clean fuel system, Air in the fuel is its Achilles heal. The ctis works nice in the cold weather and for punching through 3 foot snow drifts has become my new best friend, the good year mvt's 395 r 20's are the spec tire for Oshkosh snow removal equipment and are an excellent snow and sand tire, I could see where it might be lacking in gumbo, they have worked excellent for me. The3000 series transmissions also have proven to be more reliable stateside than in the desert. the 3126 engine also has a better rep state side than we had over there. I drove the snot out of an lmtv in the desert and also maintained them in Iraq and we had no more problems with them than any of the other trucks. aside from a few transmission harnesses,and an engine harness melting down,both problems I think were related to the extreme heat. I believe there is no need to alter the lmtv suspension for off road or un improved roads they handle the dirt and trails up here real nice, I can drive to neighboring villages 80 miles and the coffee cup will never leave the dash unless I pick it up to drink, task I couldn't do in my 1 ton. Your reasons for looking at an lmtv were the same as mine, I had to think long and hard because I cut my teeth in a duce they are near and dear to my heart I liked the a-3 more at the end of the day I believe I made the right decision with the lmtv 1 less axle,to maintain,1 less set of tires to buy, and the heater is awesome.I still haven't added cab insulation or installed my new high temp thermostat yet and I drive around in a t- shirt in the winter.

 

[justin22885]

When I look at the 5-ton what I see is a significant increase in weight, engine size, fuel consumption, etc over the other two options. Is it going to perform better off-road at 22,000lbs? In terms of LMTVs breaking down, what is generally the culprit behind this? Is it related to the reputation of poor reliability surrounding the 3116 engine that I would consider replacing anyway or is it something else?

 

[snowtrac nome]

The lmtv Has an either injection system, I have yet to have to plug mine in to start it, at a buck a kwh I don't plug in unless I have to.

 

[NDT]

What are you referring to about poor reliability of the 3116? Totally untrue.

 

[justin22885]

Well here we go again I live in Nome AK I have a lmtv set up as a service truck it has worked nice for me the cab is roomy and sealed up nice. The 3116 is quite reliable as long as you have a tight clean fuel system, Air in the fuel is its Achilles heal. The ctis works nice in the cold weather and for punching through 3 foot snow drifts has become my new best friend, the good year mvt's 395 r 20's are the spec tire for Oshkosh snow removal equipment and are an excellent snow and sand tire, I could see where it might be lacking in gumbo, they have worked excellent for me. The3000 series transmissions also have proven to be more reliable stateside than in the desert. the 3126 engine also has a better rep state side than we had over there. I drove the snot out of an lmtv in the desert and also maintained them in Iraq and we had no more problems with them than any of the other trucks. aside from a few transmission harnesses,and an engine harness melting down,both problems I think were related to the extreme heat. I believe there is no need to alter the lmtv suspension for off road or un improved roads they handle the dirt and trails up here real nice, I can drive to neighboring villages 80 miles and the coffee cup will never leave the dash unless I pick it up to drink, task I couldn't do in my 1 ton. Your reasons for looking at an lmtv were the same as mine, I had to think long and hard because I cut my teeth in a duce they are near and dear to my heart I liked the a-3 more at the end of the day I believe I made the right decision with the lmtv 1 less axle,to maintain,1 less set of tires to buy, and the heater is awesome.I still haven't added cab insulation or installed my new high temp thermostat yet and I drive around in a t- shirt in the winter.

Alright, thanks for that bit of information, it is a similar scenario and environment to what I am looking at. If it is preferable to a deuce for cold weather comfort then that translates to a lot compared to the deuce for that particular application. Does the LMTV actually fit a standard size parking space?

 

[justin22885]

What are you referring to about poor reliability of the 3116? Totally untrue.

Just something I heard, I also heard they cost more than other competing engines to maintain and repair. Cummins for example are literally everywhere and in everything and DT360/466 are in almost every bus on the road. If there is nothing wrong with the cat engine then that is fine too, I will have to do more research on them though and see how they handle cold weather.

 

[snowtrac nome]

When I look at the 5-ton what I see is a significant increase in weight, engine size, fuel consumption, etc over the other two options. Is it going to perform better off-road at 22,000lbs? In terms of LMTVs breaking down, what is generally the culprit behind this? Is it related to the reputation of poor reliability surrounding the 3116 engine that I would consider replacing anyway or is it something else?

I heard the same thing I asked my buddy at the local cat shop he told me air in the fuel system will cause injectors to fail you might get 1 o 2 changes than your cups will start to leak, if the cups start leaking the most cost effective way to repair it is replacement of the head, there are special tools to put the cups in but at their labor rates it doesn't make sense. The air usually get into the system through the priming bulb on the primary fuel filter which is not a cat part. the c-7's and 3126 have a hui pump that is more prone to failure. The one other problem is the cost of the tooling to do the overhead but my cat guy says its really only required every 100k.

 

[mkcoen]

Does the LMTV actually fit a standard size parking space?

Here's mine at Whataburger. The bumper is over the sidewalk but the tailgate is inside the space. It was tough to do that with my 4 door F-250.

 

[snowtrac nome]

you will pay the same for cummins parts and service as you do cat, all the major manufactures have taken parts supply agreements away from the after market, and if want real expense buy some electronic parts for one of the new electronic engines,

 

[justin22885]

Here's mine at Whataburger. The bumper is over the sidewalk but the tailgate is inside the space. It was tough to do that with my 4 door F-250.


View attachment 712729

I will admit that even my Dakota will often have the rear of the bed past the lines of the parking spaces. It might even be easier to line up properly with the flat nose and better visibility? Do they have power steering?

 

[Aernan]

If you plan on doing a lot of cold weather starting of the truck it will certainly cause wear until the engine gets warm enough to oil everything. The ether system certainly will work for starting but warming the block is ideal.

My truck has the ether system fitted but I plan on adding a diesel hydronic furnace to also be used with a living space. Advantage is it heats the coolant so the cab air will be warm at the same time it's ready to start the engine.

Regarding reliability of the 3116. Compared with a GAS engine it will last practically forever. It's plenty reliable. Compared with other industrial diesel motors the complaints are:

The block is bored directly not sleeved. So that means you need to remove the engine from the frame to re-bore/rebuild the motor. Due to cost it's likely you would just swap the engine with NOS or used. The engine is certainly possible to rebuild. Other diesels can have sleeves. It seems if you have sleeved cylinders you can remove/replace them with the engine still fitted.
Further the cylinders aren't fully surrounded by coolant. This makes it possible to overheat the cylinders easier. After overheat you will get massive blowby and the rings need replacement and possibly re-bore the cylinder which is costly.

If the turbo seal goes it the metal will go further into the engine causing all kinds of problems.

On HUI (3126) the HUI pump can go and blow metal farther into the engine. No risk on the MUI 3116.

From what I am hearing the folks in the military like to remove the engine governor and drive around in hot weather. As you can imagine doing this will overheat the engine quickly. I have had more than one person tell stories of driving the trucks at 85 Mph or above. I don't believe they were changing the final drive ratio with gearing so I'm guessing it was governor delete that allowed such high speeds.

 

[justin22885]

I heard the same thing I asked my buddy at the local cat shop he told me air in the fuel system will cause injectors to fail you might get 1 o 2 changes than your cups will start to leak, if the cups start leaking the most cost effective way to repair it is replacement of the head, there are special tools to put the cups in but at their labor rates it doesn't make sense. The air usually get into the system through the priming bulb on the primary fuel filter which is not a cat part. the c-7's and 3126 have a hui pump that is more prone to failure. The one other problem is the cost of the tooling to do the overhead but my cat guy says its really only required every 100k.

What head has to be replaced? The cylinder head? And what is the solution to the cups going bad or for more reliably preventing air leaks?

 

[justin22885]

If you plan on doing a lot of cold weather starting of the truck it will certainly cause wear until the engine gets warm enough to oil everything. The ether system certainly will work for starting but warming the block is ideal.

My truck has the ether system fitted but I plan on adding a diesel hydronic furnace to also be used with a living space. Advantage is it heats the coolant so the cab air will be warm at the same time it's ready to start the engine.

Regarding reliability of the 3116. Compared with a GAS engine it will last practically forever. It's plenty reliable. Compared with other industrial diesel motors the complaints are:

The block is bored directly not sleeved. So that means you need to remove the engine from the frame to re-bore/rebuild the motor. Due to cost it's likely you would just swap the engine with NOS or used. The engine is certainly possible to rebuild. Other diesels can have sleeves. It seems if you have sleeved cylinders you can remove/replace them with the engine still fitted.
Further the cylinders aren't fully surrounded by coolant. This makes it possible to overheat the cylinders easier. After overheat you will get massive blowby and the rings need replacement and possibly re-bore the cylinder which is costly.

If the turbo seal goes it the metal will go further into the engine causing all kinds of problems.

On HUI (3126) the HUI pump can go and blow metal farther into the engine. No risk on the MUI 3116.

From what I am hearing the folks in the military like to remove the engine governor and drive around in hot weather. As you can imagine doing this will overheat the engine quickly. I have had more than one person tell stories of driving the trucks at 85 Mph or above. I don't believe they were changing the final drive ratio with gearing so I'm guessing it was governor delete that allowed such high speeds.

Hmm, all of this sounds like the 3116 is a bad engine for what I want. I am not looking for a vehicle to drive for a few years and replace, but something I could improve upon over the years, tailor it to what I want, and drive it the rest of my life. This would mean I will likely find myself having to do engine work from time to time and having to remove the engine to replace it or do a rebuild just isn't something I am going to want to have to do. I would prefer something that can be rebuilt in the frame. And I wouldn't mind an engine that is more used meaning more salvage yards and Craigslist ads might have the parts I am looking for when it comes to improvements or repairs. I may still want to look into the 5.9 cummins, DT360 or 466, or some other option.

 

[Aernan]

If you don't overheat the engine you should get some 500k miles out of it. There are lots of new old stock and used motors on the market right now.

Regarding the fuel injection system:

On newer (read more expensive) engines replacement of a single injector (not uncommon) requires no special tooling but the injectors are $600-$800 each. You may need to change the cup between the injector and the head.

On the 3116 if you change an injector you must change the fuel cup and it involves a special tool to crush the injector to the right depth. The cup is just a special crush washer. Also you will need to re-sync the fuel injector mechanical linkage.

To adjust the fuel system there are special (expensive) cat only tools.

From what I am reading the valves need adjusted or checked at 30k then 60k then 100k and every 100k after that I believe. In one of those intervals it's good to re-sync the fuel system (mechanical injectors) along with setting idle, max RPM and engine timing. All of that (except sync fuel linkage) can be done with conventional hand tools but there are CAT specific tools to make the job easier.

If you get a A1 variant of the FMTV then you get the electronic engine which simplifies this. Ultimately I believe they ended up using the cat C7 engine in really new trucks. I would expect you could retrofit it or pay a premium to get a truck with a newer engine. The downside is the A1 and newer have smog emissions equipment. Specifically DPF and DEF tank.

If you really want the simplicity of the electronic engine you could hunt for a 3116e before they rebadged it 3126. It may also be possible to retrofit the HUI and ECU into the 3116 but I haven't looked deep into that.

I plan on building an expedition vehicle onto my M1078. I'm really enjoying the simplicity and long service interval of this Cat engine. I know I can do the valve adjustments and am planning on having a cat dealer do the 60k service (I'm at 16k right now) to make certain the engine is in good shape. If I can find a set of the fuel sync tools cheap enough I will buy them and do it myself. I know cat has special software for the ECU and I have not seen anyone talking about owning this personally. You may want to ask if you can get ECU tuning software for the other engines you are looking at.

 

[snowtrac nome]

the block on a 5.9 is the same as a 3116 no sleeves I own one of those too they don't have the torque out of the box the 3116 has and juicing them up will also shorten the life of them I only got 500 k out of my 12 valve. the hydronic heater is a good idea and also something I'm looking at. The air in the fuel system can be cured with a good cat primary filter water separator and a cat primer pump. I haven't done mine yet because its still working good. A change from 15w40 to a 5w40 synthetic will improve your oiling performance when cold and is an approved lubricant for cooler temps I believe up to 80 degrees and down to -30. Taken care of it should be a million mile motor. The problems you hear of are usually the result of abuse or contaminated fuel these problems will also plague the cummins cornbinder and Detroit engines. It is a great cold weather engine when outfitted right just that the low pressure injection means it starts like an 855 cummins when cold and there are several cold weather starting aids used on them the military chose to use either injection its simple and works well maybe I will remember to take a video tomorrow when I start it up

 

[snowtrac nome]

If you don't overheat the engine you should get some 500k miles out of it. There are lots of new old stock and used motors on the market right now.

Regarding the fuel injection system:

On newer (read more expensive) engines replacement of a single injector (not uncommon) requires no special tooling but the injectors are $600-$800 each. You may need to change the cup between the injector and the head.

On the 3116 if you change an injector you must change the fuel cup and it involves a special tool to crush the injector to the right depth. The cup is just a special crush washer. Also you will need to re-sync the fuel injector mechanical linkage.

To adjust the fuel system there are special (expensive) cat only tools.

From what I am reading the valves need adjusted or checked at 30k then 60k then 100k and every 100k after that I believe. In one of those intervals it's good to re-sync the fuel system (mechanical injectors) along with setting idle, max RPM and engine timing. All of that (except sync fuel linkage) can be done with conventional hand tools but there are CAT specific tools to make the job easier.

If you get a A1 variant of the FMTV then you get the electronic engine which simplifies this. Ultimately I believe they ended up using the cat C7 engine in really new trucks. I would expect you could retrofit it or pay a premium to get a truck with a newer engine. The downside is the A1 and newer have smog emissions equipment. Specifically DPF and DEF tank.

If you really want the simplicity of the electronic engine you could hunt for a 3116e before they rebadged it 3126. It may also be possible to retrofit the HUI and ECU into the 3116 but I haven't looked deep into that.

I plan on building an expedition vehicle onto my M1078. I'm really enjoying the simplicity and long service interval of this Cat engine. I know I can do the valve adjustments and am planning on having a cat dealer do the 60k service (I'm at 16k right now) to make certain the engine is in good shape. If I can find a set of the fuel sync tools cheap enough I will buy them and do it myself. I know cat has special software for the ECU and I have not seen anyone talking about owning this personally. You may want to ask if you can get ECU tuning software for the other engines you are looking at.

I own a dealer version of cat e-t but I do this stuff for a living I also have deere case cummins Detroit and perkins. its not cheap if I have to plug in you will pay but our dealers are a $600.00 plane ticket away plus an overnight trip just to plug in it makes sense for me to have it. you can scan codes and do most maintenance on the 3126 with a prolink .If you have a c-7 you will have to have cat e-t to change an injector, likewise if you have an isb or isc cummins the same goes with those,you have to have a laptop to load in the new flow rates for the injectors.