LMTV Alternator Disaster, engine now catastophic

[ogdobber]

Hey guys new to the forum,
Picked up my m1078 fresh off the boat in San Diego from Hawaii. My front driveshaft was bent from presumably a forklift, knew this when I bought it but figured worst case I could pull it off and just drive with the rear until it was fixed. I however just left it on and drove below 35mph to north county (to minimise the vibrations). When I did pull the front driveshaft the truck would only move in “mode” on the Allison selector. Are these things normally fwd??
Anyways I had the front driveshaft retubed and balanced and headed up to Los Angeles, just passed Oceanside, right along Camp Pendleton, BAM then warning lights to stop and temp.
Alternator fell off and collected all the belts. Hence what lead me here trying to find the big bolt size for the alt. Anyways 4 hours later on the side of the freeway I got a gates belt on the water pump and turned around back home.
There was still a slight vibration however nothing close to what it was before. It’s possible all the “damage” was when I drove it the initial 30 miles under bad vibration and what I have now was just the icing on the cake?? Not sure but getting it all back together in a few days when I get parts.
I think after reading this entire thread I’m going to pull the front and rear shafts and take them down to a driveline shop in El Cajon.
One question hopefully someone can answer, when the shop near me retubed, I’m not confident it’s the same length (or correctly balanced). Seems the spline part might be further out?
Can someone measure the tube length for me? Weld to weld


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[Kbarnes0]

Hey guys new to the forum,
Picked up my m1078 fresh off the boat in San Diego from Hawaii. My front driveshaft was bent from presumably a forklift, knew this when I bought it but figured worst case I could pull it off and just drive with the rear until it was fixed. I however just left it on and drove below 35mph to north county (to minimise the vibrations). When I did pull the front driveshaft the truck would only move in “mode” on the Allison selector. Are these things normally fwd??
Anyways I had the front driveshaft retubed and balanced and headed up to Los Angeles, just passed Oceanside, right along Camp Pendleton, BAM then warning lights to stop and temp.
Alternator fell off and collected all the belts. Hence what lead me here trying to find the big bolt size for the alt. Anyways 4 hours later on the side of the freeway I got a gates belt on the water pump and turned around back home.
There was still a slight vibration however nothing close to what it was before. It’s possible all the “damage” was when I drove it the initial 30 miles under bad vibration and what I have now was just the icing on the cake?? Not sure but getting it all back together in a few days when I get parts.
I think after reading this entire thread I’m going to pull the front and rear shafts and take them down to a driveline shop in El Cajon.
One question hopefully someone can answer, when the shop near me retubed, I’m not confident it’s the same length (or correctly balanced). Seems the spline part might be further out?
Can someone measure the tube length for me? Weld to weld


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The Allison transmission/transfercase are combined. In normal operation It splits the ratio 30/70 front to rear. Im Mode, It locks the ration 50/50. It will cause damage if operated w/o a driveline in.

@coachgeo has a great set of links at the bottom of his signature. From what I have read, the vibrations can be detrimental to a number of items. You encountered one. The front timing cover bolts would be next to check for torque.

If you havent yet, I would run through and grease everything up on all the Zirc points on the rig. The drivelines have 2 fittings at each u joint. and one at the slip joint.

Ill grab a measurement if i head down to the shop.

 

[coachgeo]

......

@coachgeo has a great set of links at the bottom of his signature. .....

Cant claim any credit for this one. The links are NOT in my sig. line.... they are in Awsomeness sig line.

see his sig line below his July 6th? recent post ..... link below

U-Joint bolts...

Well I need some new U-joint bolts... and I am having a heck of a time finding them. Now the military uses a break away type and I have only found some on the e auction place and the seller wants like 14 bucks each.... I aint doing that. I am looking for the Spicer 5-73-109 that is used with...

steelsoldiers.com

there is also the parts spread sheet that is a sticky on top of this FMTV forum page

there is ton of links to information and parts on the LMTV MTV facebook group page.

Log into Facebook

Log into Facebook to start sharing and connecting with your friends, family, and people you know.

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[Kbarnes0]

Cant claim any credit for this one. The links are NOT in my sig. line.... they are in Awsomeness sig line.

Face palm... dang. Thought I was getting someone headed in the right direction. Either way, It came around ... Ill do better next time

 

[NDT]

Weld to weld front ds is 14.5”

 

[ogdobber]

Well shoot, seems like a alternative universe with the same story. Tracked down my oil leak. Cracked block. That’s right behind the exhaust down pipe. Any advice on a new engine would be appreciated

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[Tow4]

Cracked blocks suck.

Draw a vacuum on the crankcase breather, make sure to pull a vacuum the whole time you are working on it. Spray the cracked area liberally with brake cleaner. Grind the crack, spray again with brake cleaner and apply JB weld to the crack. I fixed a Mazda 12A rotary engine this way and it went 50K more miles before I sold the car.

Of course if you don't need to drive the truck, just look for a new engine.

 

[Awesomeness]

Well shoot, seems like a alternative universe with the same story. Tracked down my oil leak. Cracked block. That’s right behind the exhaust down pipe. Any advice on a new engine would be appreciated

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That's exactly how my block cracked.

There are a lot of people parting these out now, and you should be able to find an engine for it. Make sure to get the driveshafts balanced before you put the new engine in.

 

[ogdobber]

Cracked blocks suck.

Draw a vacuum on the crankcase breather, make sure to pull a vacuum the whole time you are working on it. Spray the cracked area liberally with brake cleaner. Grind the crack, spray again with brake cleaner and apply JB weld to the crack. I fixed a Mazda 12A rotary engine this way and it went 50K more miles before I sold the car.

Of course if you don't need to drive the truck, just look for a new engine.

Thanks that’s great advice. I’m going to need to drive it about ~80 miles to pull the engine (rather than do it in my driveway )


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[ogdobber]

That's exactly how my block cracked.

There are a lot of people parting these out now, and you should be able to find an engine for it. Make sure to get the driveshafts balanced before you put the new engine in.

Interesting. Driveshafts are getting rebuilt as I speak


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[Reworked LMTV]

That's exactly how my block cracked.

There are a lot of people parting these out now, and you should be able to find an engine for it. Make sure to get the driveshafts balanced before you put the new engine in.

Where is this on the block?

 

[ogdobber]

Where is this on the block?

Passenger side right behind the exhaust down pipe and it goes from the oil pan up 3 maybe 4 inches


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[mkcoen]

If you were on the east coast I'd say contact Suprman about an engine but that'd probably be pricey to ship across the country.

 

[Reworked LMTV]

If you were on the east coast I'd say contact Suprman about an engine but that'd probably be pricey to ship across the country.

Yes, go with Supraman. He's a good guy and will make it happen foryou.

 

[spankybear]

I'd do the JB weld... I have fixed blocks with JB weld in the past and yes it worked.

 

[Asymair95]

Another gentleman used a product called “Lock and stitch” which worked great for him. Not sure if was a welding or brazing product, but he said it is very strong. He really uses his truck too (unlike me), and hauls heavy loads and such. So far it has held up well. Just another option for you.

 

[Awesomeness]

None of those are going to be good structural solutions long term. The blocks crack at a critical stress point, where the engine bolts to the transmission bell housing. If you plan to do anything other than driving it to a repair facility, or maybe just parades for the rest of its life, you're going to want to either get it welded or replace the engine.

 

[ogdobber]

Well patched up the crack with jb weld (just to get to the shop because that engine is coming out) got my new driveshafts and they are butter smooth however as far as engines I can go a couple different routes...
I can buy a low mileage 3116 or rebuild what I got with a virtually free block. What do you guys think?
If I rebuild I’ll do rings, bearings, seals etc. Is it important to use oe cat parts? Or is another brand good? And what else should be done as long as this can of worms is open?
Used takeout engine would sure be easy tho, just spray it fresh yellow and call it a day.
Thanks, Appreciate you guys.


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[coachgeo]

Well patched up the crack with jb weld (just to get to the shop because that engine is coming out) got my new driveshafts and they are butter smooth however as far as engines I can go a couple different routes...
I can buy a low mileage 3116 or rebuild what I got with a virtually free block. What do you guys think?
If I rebuild I’ll do rings, bearings, seals etc. Is it important to use oe cat parts? Or is another brand good? And what else should be done as long as this can of worms is open?
Used takeout engine would sure be easy tho, just spray it fresh yellow and call it a day.
Thanks, Appreciate you guys.


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if your spending coin anyway.... and dont have a preference for mechanical injection..... just get an appropriate C7 and add a few wires... Or heck.... go with a cummins 617 I believe was the variant the commercial version of these trucks was sold with. the ol' turn a lemon situation into lemonade adage.