Top 5 fixes to your LTMV

[TheRealJohnnyB]

Hey guys - I'm working on a new build over here and curious to know what your top 5 fixes would be?

On the 3116, the oil line of death for sure.

Other I would think would include

Secondary trans cooler delete
New battery cables (the corrosion gets bad on these!)
All new front end bushings/steering linkages
New cab air springs is a must for the wife

Next up, balance drive shafts and ecohubs.

 

[Ronmar]

Hey guys - I'm working on a new build over here and curious to know what your top 5 fixes would be?

On the 3116, the oil line of death for sure.

Other I would think would include

Secondary trans cooler delete
New battery cables (the corrosion gets bad on these!)
All new front end bushings/steering linkages
New cab air springs is a must for the wife

Next up, balance drive shafts and ecohubs.

On a 3116 I would(and did) re plumb the engine cooling back to the way cat designed it. As it is now the plumbing sends all the bypass coolant down to the trans cooler instead of back thru the engine to get the engine to proper op temp. Running a diesel too cold is not good for it. As plumbed the engine will not warm up until the transmission becomes a heat source.

Cat originally had the bypass coolant coming out the bottom of the housing and right back into the top of the water pump. they left it the way cat designed it on the 3126 and C7 lMTVs

I ran my heater return line down to the port on top of the cooler, so I can send fluid down there if I wish/when its cold out. the engine now warms right up to op temp. You can modify the existing thermostat housing by cutting the cast elbow off and you will need a cat water pump. This mod also allows you to go back to the cat pump(easilly sourced, there are 2 types) as opposed to the modified one required for the LMTV(not so easy to find) or having to modify one(cut of bypass input pipe and install freeze plug). I did a utube video on this mod under user name rronmar.

 

[wheelspinner]

The air compressor bracket!!!! Make SURE it’s tight and use locktite

 

[GeneralDisorder]

ECO hubs (#1 with a bullet)
Cruise Control
Factory style A1P2 air conditioning
370 HP ECM flash
Gen 1 HIMARS turret hatch.

 

[fuzzytoaster]

From doing several hundred FMTV of all variants, ages, etc..

1. New fuel hoses (there are 3)
2. Rebuild cab lift pump/reseal cab latch
3. Run second ground from 24v (-) direct to chassis
4. Inspect/clock/balance drive shafts
5. Inspect/replace rubber fan bushing if required

Neglecting any of these 5 will eventually lead to a major failure.

 

[GeneralDisorder]

From doing several hundred FMTV of all variants, ages, etc..

1. New fuel hoses (there are 3)
2. Rebuild cab lift pump/reseal cab latch
3. Run second ground from 24v (-) direct to chassis
4. Inspect/clock/balance drive shafts
5. Inspect/replace rubber fan bushing if required

Neglecting any of these 5 will eventually lead to a major failure.

These are all good too. Down to semantics but I would call these preventative maintenance. Fixing to me addresses something that is broken or missing. Fine lines between preventative maintenance, fixes, upgrades, and modifications. They all land on a spectrum somewhere for sure but fuel hoses aren't glamorous so didn't really occur to me to list them in my top since the OP was including ECO hubs and trans cooler delete, etc.

Another BIG one that gets neglected - air dryer service.

 

[olly hondro]

Bypass the reverse polarity box. Gain 0.7 volts diode drop, lose a common corrosion location.

Delete one of the two series battery strings. Running two batteries is easier on the goofy dual voltage alternator. The exception would be for large electrical load application, such as a shelter, obnoxious off road light suite, or heavy winching.

 

[Awesomeness]

A good readthrough here in the Common Problems-Fixes document in my signature.

 

[olly hondro]

Front gladhand delete. Nearly every "How come my brakes don't work right?" problem traces back to one of the three pneumatic valves that support front glad hand functionality.

 

[Awesomeness]

Front gladhand delete. Nearly every "How come my brakes don't work right?" problem traces back to one of the three pneumatic valves that support front glad hand functionality.

Preventative maintenance on it, or replacing it, would be of similar difficulty, and allow you to keep it.

 

[GeneralDisorder]

Preventative maintenance on it, or replacing it, would be of similar difficulty, and allow you to keep it.

Agree. Wouldn't delete them. We have a good community/network of FMTV and other military vehicles throughout the country on this forum and the facebook groups, etc and some of us have tow bars, air hoses, and interconnect cables that can allow us to rescue or be rescued. Not having the front glad hands would make that needlessly harder.

Yes there are several one way and two way check valves that should be replaced once every two decades.

I wouldn't delete any of the glad hands or the NATO slave receptacle.

 

[fuzzytoaster]

These are all good too. Down to semantics but I would call these preventative maintenance. Fixing to me addresses something that is broken or missing. Fine lines between preventative maintenance, fixes, upgrades, and modifications. They all land on a spectrum somewhere for sure but fuel hoses aren't glamorous so didn't really occur to me to list them in my top since the OP was including ECO hubs and trans cooler delete, etc.

Another BIG one that gets neglected - air dryer service.

I agree they are or should be preventative but by the time we get them it's mandatory. *cough* I mean the Army totally follows all PMCS by the TM of course! *cough*

 

[TheRealJohnnyB]

On a 3116 I would(and did) re plumb the engine cooling back to the way cat designed it. As it is now the plumbing sends all the bypass coolant down to the trans cooler instead of back thru the engine to get the engine to proper op temp. Running a diesel too cold is not good for it. As plumbed the engine will not warm up until the transmission becomes a heat source.

Cat originally had the bypass coolant coming out the bottom of the housing and right back into the top of the water pump. they left it the way cat designed it on the 3126 and C7 lMTVs

I ran my heater return line down to the port on top of the cooler, so I can send fluid down there if I wish/when its cold out. the engine now warms right up to op temp. You can modify the existing thermostat housing by cutting the cast elbow off and you will need a cat water pump. This mod also allows you to go back to the cat pump(easilly sourced, there are 2 types) as opposed to the modified one required for the LMTV(not so easy to find) or having to modify one(cut of bypass input pipe and install freeze plug). I did a utube video on this mod under user name rronmar.

Awesome channel -Thanks for sharing! Cat pump is a must.

Love the cab lift setup btw, totally steeling that! Cheers

 

[olly hondro]

Delete the hydraulic kneeling circuit. I understand some of us still load their FMTV onto C130s so need it, but for the rest of us it is useless complexity.

I considered splitting the circuit then using the cylinders as suck down winches, but got over it.

 

[Awesomeness]

Delete the hydraulic kneeling circuit. I understand some of us still load their FMTV onto C130s so need it, but for the rest of us it is useless complexity.

I considered splitting the circuit then using the cylinders as suck down winches, but got over it.

The kneeling hydraulic cylinders could be repurposed/replaced with cylinders to do something else useful, such as extend an awning, deploy stairs, or lift a fuel can rack.

 

[MatthewWBailey]

ECO hubs (#1 with a bullet)
Cruise Control
Factory style A1P2 air conditioning
370 HP ECM flash
Gen 1 HIMARS turret hatch.

Just a side question here, does the HP upgrade only require an ECM flash? My '04 A1 shows 275 HP on the computer (which Cat said they can't boost to 335HP per the actual nameplate because "it's illegal") but since the engine says 335HP, I'd like to be up at that number because I have trouble maintaining 45mph up 6% road grades at 7000' elevation. Is it just an ECM flash or do I need injectors and a bigger turbo? Cat guys were very 'catty' about the details

 

[GeneralDisorder]

Just a side question here, does the HP upgrade only require an ECM flash? My '04 A1 shows 275 HP on the computer (which Cat said they can't boost to 335HP per the actual nameplate because "it's illegal") but since the engine says 335HP, I'd like to be up at that number because I have trouble maintaining 45mph up 6% road grades at 7000' elevation. Is it just an ECM flash or do I need injectors and a bigger turbo? Cat guys were very 'catty' about the details

Your truck is the 3126b engine?

It's not illegal to flash it to the 330 HP map - you can pay CAT corporate for a "rerate" if you talk to the right people. Or you can send me your ECM and I can do it for $600 and also change any other features like turning on cruise control, and correcting for ECO hubs or 3.07 gears, etc. Often I find that the CAT people are unfamiliar with our trucks and either unwilling to touch them, or they screw it up - I have found that a fair number of these trucks - especially the 3126b trucks will not accept a flash though the truck's wiring harness and when that happens the CAT dealer will likely have no choice but to make you buy a new ECM programmed by corporate for $3k because they are not equipped to bench flash an ECM outside of the truck. And when that happens it wipes the ECM and the truck is a lawn ornament till you get a replacement. This can be corrected if you pull the ECM and use bench flashing tools but again - dealers are not equipped for that level of service.

The only hardware modification the 3126b requires for the 330 HP tune is adding the atmospheric pressure sensor. There's already a harness connector present for it. You just screw it into the port on the engine and plug it in. Takes 10 minutes. Turbo and injectors and all that are identical. You are just changing the tune to the MTV map.

The 370 HP map is for the C7. Same rules apply as above but it doesn't require the sensor - all C7's already have it. The C7 can be rated at 275, 330, or 370 HP all using the same hardware.

 

[MatthewWBailey]

I don't know if it's 3126 or 3126b. See Pics of engine. I don't trust Wagner Cat bc they charge $500 to say hello. Those 2 knuckle heads that looked at the engine thru their PC couldn't change a spare tire on a Yugo. The service manager said EPA rules prevent them.

 

[GeneralDisorder]

I don't know if it's 3126 or 3126b. See Pics of engine. I don't trust Wagner Cat bc they charge $500 to say hello. Those 2 knuckle heads that looked at the engine thru their PC couldn't change a spare tire on a Yugo. The service manager said EPA rules prevent them.

The military only use the 3126b. The 3126 (non "b") was back in ~96-98 and the military was still using the 3116. The 3126b was introduced in 1999 and that's when the military began adopting it.

EPA rules don't apply to defense engines. The service manager is wrong and if he actually contacted CAT they would inform him of such. @Lostchain got the CAT equipment dealer to rerate his 2003 and CAT corporate allowed it to be rated to 330 HP. Yours would be no different. At the dealer level corporate has to give them the files and allow the rerate to happen - it's all done while their laptop is connected to SIS and if SIS allows it or they call dealer support and they allow it then it's legal. It's all based on the serial number of the engine and if he didn't call corporate with your serial then he's just talking out his anus.

You can pull your ECM and send it to me and I'll turn it around in 24 hours.

 

[MatthewWBailey]

The military only use the 3126b. The 3126 (non "b") was back in ~96-98 and the military was still using the 3116. The 3126b was introduced in 1999 and that's when the military began adopting it.

EPA rules don't apply to defense engines. The service manager is wrong and if he actually contacted CAT they would inform him of such. @Lostchain got the CAT equipment dealer to rerate his 2003 and CAT corporate allowed it to be rated to 330 HP. Yours would be no different. At the dealer level corporate has to give them the files and allow the rerate to happen - it's all done while their laptop is connected to SIS and if SIS allows it or they call dealer support and they allow it then it's legal. It's all based on the serial number of the engine and if he didn't call corporate with your serial then he's just talking out his anus.

You can pull your ECM and send it to me and I'll turn it around in 24 hours.

Works for me. I'm not using Cat service anymore. Can you send me you shipping info?