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LMTV Alternator Disaster, engine now catastophic

aleigh

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Phoenix, AZ & Seattle, WA
I don't know what failed, but the oil sure left in a hurry. It was dripping off the rear mud flap. Weirdly none of the local tow companies were willing to move anything heavy at 9pm so I had to leave it, so I'll arrange to get it moved later today, and maybe take a closer look. It's kind of a shame it's such a mess oil wise, because it's going to make a mess wherever I park it, which is kind of a problem. I feel like if the engine is going to lunch it at least could have the grace to do it without becoming a superfund site.

At a certain point, as to what happened, who knows. It did get overheated back in Oregon (the start of all this), so maybe the block cracked or some bearing got cooked and it just took this long to work itself into a disaster. Maybe that class 2 leak it developed shortly before the trip was a crack and it took this long. I don't know. I do know it sucks because I just put a ton of time and money into fixing it, but c'est la vie I guess. I'm trying not to be upset about it. The title of this thread might as well be "disaster" haha what a terrible trip. AND I missed the superbowl.

My girlfriend isn't too torn up about it though - now I get to fly home!
 

snowtrac nome

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western alaska
I just ran into a problem, the line going to the oil sampling valve had been rubbing on the oil filter, in my case it wore through the line first, but had left a deep wear mark in the oil filter to.
 

Pointman0853

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Gardnerville, NV
After reading all of the shared testing info from post #56, It looks like the conclusion is that the CV driveshaft was the recommended unit to eliminate the acceleration issues causing the destructive and restrictive vibrations.
As I live in the Reno/Sparks area I plan on investigating this as an option locally, as replacing things that may fall off/break and going through the trouble don't equal a reliable adventure rig...

Pointman
 

Awesomeness

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Orlando, FL
Another thing I've forgotten to mention about my driveshafts is that the rear one had cardboard in it. The driveshaft guys said it's called a "tube deadener", and is intended to reduce vibrations. They took it out of my shaft, and did not replace it because they said it shouldn't be used on shafts less than 20" longer than the rear LMTV shaft. Over time the cardboard deteriorates and flops around inside the shaft, making it difficult to balance in the shop and then it can unbalance itself in the field.

You can see them on page 16 of this Spicer catalog: https://www.drive-lines.com/catalogs/pdf/dana/J300P-9.pdf
 

expeditionnw

Member
174
1
18
Location
Alaska
After reading all of the shared testing info from post #56, It looks like the conclusion is that the CV driveshaft was the recommended unit to eliminate the acceleration issues causing the destructive and restrictive vibrations.
As I live in the Reno/Sparks area I plan on investigating this as an option locally, as replacing things that may fall off/break and going through the trouble don't equal a reliable adventure rig...

Pointman
i beleive all the issues the thread originator has had would have been mitogated by a painstakingly thorough inspection of tge truck, with the idea that every bolt may be hamd tight, and hoses may be routed incorrectly. Every single truck I have owned has needed this. You just never know what was removed or loosened for no discernable reason.
 

tennmogger

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Greenback, TN
i beleive all the issues the thread originator has had would have been mitogated by a painstakingly thorough inspection of tge truck, with the idea that every bolt may be hamd tight, and hoses may be routed incorrectly. Every single truck I have owned has needed this. You just never know what was removed or loosened for no discernable reason.
Yes! I just toasted an engine on a new-to-me LMTV because the slight bouncing in the oil pressure gauge was a loosening sending unit (losing ground) which I missed, and that cost an engine when the sender blew out at speed..
 

aleigh

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Location
Phoenix, AZ & Seattle, WA
Where are you having your truck towed to? Let me know when your back in town if I’m free I’ll turn a wrench.
It's parked at a friends in Bellingham. I haven't decided if I'll do the swap myself or just have it towed to a diesel place to get it done (since I can do that from Arizona). I need to take a deep breath and go through the what-next... Another 3116 (used, reman, NOS), or go up to a 3126 or C7 and the attendant benefits and complexity. Or swap for just something else entirely. It's a SAE #2 I think a lot of engines would fit in there.

I don't, you know, love the fuel economy, and if a newer engine is going to be more efficient it might pay for itself since it needs a new engine anyways... I need to look into it anyways. I'm trying to see this as an opportunity to get exactly what I want for a truck that I intend to own for the long-term.
 
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coachgeo

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North of Cincy OH
Yes! I just toasted an engine on a new-to-me LMTV because the slight bouncing in the oil pressure gauge was a loosening sending unit (losing ground) which I missed, and that cost an engine when the sender blew out at speed..
Sorry to hear of your plight. was that your 95?
 

Pointman0853

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Gardnerville, NV
We bought our M-1078 from a Private party in Pennsylvania 2-years ago. After assurances that it was in good shape, we decided to drive it home to Gardnerville, NV. First issue was in Indiana in cold weather and involved loose coolant hose clamps. Tightened all of them and we were good until Wyoming when we had coolant inside the cab due to loose hose clamps in the heater box. A 30-min roadside fix and we were back on our way. I do grease and check things frequently. I have replaced the front prop shaft with an A-1 unit which solved some vibration issues, but now I suspect the rear...

I did make contact with the drive-line experts in Sparks yesterday. They rebuild prop shafts on the big 5-ton NV Energy 4x4 and 6x6's. They stated the double-cardan jointed prop-shafts are prohibitively expensive. He also told me that it would be a challenge to create a CV based prop-shaft as the major manufacturer is GKN and their primary business is with OEM manufacturers and they do not play well with aftermarket needs. Plus, we would need to create the yoke adaptors to work with the CV joints, etc./

I verified that I do have the initially upgraded rear A-0 prop-shaft. That being said, I plan to pull it and have it looked at in an effort to insure that I will have cleared that as a cause of drive-line vibrations at speeds above 50 mph.

Pointman
 
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coachgeo

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North of Cincy OH
...
I did make contact with the drive-line experts in Sparks yesterday. They rebuild prop shafts on the big 5-ton NV Energy 4x4 and 6x6's. They stated the double-cardan jointed prop-shafts are prohibitively expensive. He also told me that it would be a challenge to create a CV based prop-shaft as the major manufacturer is GKN and their primary business is with OEM manufacturers and they do not play well with aftermarket needs. Plus, we would need to create the yoke adaptors to work with the CV joints, etc./....
Pointman
hmmm... things have changed in sparks. My CV jointed shaft made there was not bad at all. Granted that was a Jeep and back in hmmm. 1998??? I see they are still there. This is whom I used way back then

http://drivelineandgear.com/
 
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Awesomeness

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hmmm... things have changed in sparks. My CV jointed shaft made there was not bad at all. Granted that was a Jeep and back in hmmm. 1998??? I see they are still there. This is whom I used way back then
http://drivelineandgear.com/
My guess would be that Jeep shaft is just a different animal. On smaller vehicles, there are a lot of parts and options out there to cobble together something. With these, there is only 1 medium duty truck on the road for what, every 10,000 consumer vehicles sold? So there are going to be far fewer sources to build from. I'm not saying it's impossible, but Pointman's response is exactly what I expected to hear. I was anticipating that we would either need to find a very specialized driveshaft maker accustomed to the atypical needs (e.g. one that makes driveshafts for some obscure niche market like monster trucks or extreme farming / construction equipment), or design the components ourselves (sounds like another awesome project, but one of many on my "list").

I think, as the Army has decided on and found to be largely true, that you can get decent results from the regular driveshaft. In fact, those of us having issues are essentialy re-experiencing something that the Army found and "fixed" long ago. So in essence we are finding a new variant of the problem, where the "fixed" heavier-duty driveshafts eventually are able to cause similarly destructive vibration scenarios to the original smaller shafts. It's probably the sum of several stacked effects, over the course of many years, such as spline wear leading to lateral movement ("hinging"), u-joints wearing and allowing a little play, other components such as the pinion bearings wearing and adding a little more play to the mix, etc. You add all these things up, over 10-20 years, and you get an elusive vibration that manages to cause a small vibration... that vibration is then enough to start affecting things, such as increasing the shaft runout and imbalance, loosening a u-joint bolt, wallowing out a u-joint cap hole in the yoke, beating on the bearings in the u-joint, and the vibration increases. It's an upward spiral, until it reaches a point that it breaks something.

We know anecdotally and from the military reports that the FMTV is sensitive to vibration issues. To put it another way, the safety margin is small. The original FMTVs had issues, and the Army's fix pushed it back in the black, but by how far? You add up decades of tiny wear and tear on parts, and you creep back across the line into the danger zone.

The logical takeaways to me are:

1.) If you bought a new FMTV, take the driveshafts in to be balanced, have the u-joints replaced, and have the cardboard in the rear shaft removed (or replaced). Use thread locking adhesive (e.g. LocTite blue) and install safety tab washers on all the u-joint bolts, while torquing them to 17-24 ft*lb. I would recommend thread locking adhesive on the alternator, starter, and air compressor bolts too, since once they loosen it beats itself apart.

2.) If you break an extremity engine accessory (e.g. water pump, alternator bracket, starter mount, air compressor / front engine cover, fan clutch / blade, etc.) in a mechanically violent way (e.g. it cracks or breaks off, as opposed to wearing through, rusting, or losing a rubber seal / hose), keep a close eye on it, and you are wise to have your driveshafts balanced as soon as possible.

3.) If you break multiple extremity engine accessories within a very short amount of time (e.g. a tank of gas = 250 miles), stop all driving over 30 MPH until the driveshafts can be balanced.

At worst, you're out $200 for driveshaft balancing to gain the peace of mind that nothing is wrong with them and it was just coincidental broken things. At best, you save yourself the cost of replacing an engine and/or transmission, which with labor is roughly the cost of the whole truck (my total replacement was in the neighborhood of $7000 out of pocket, on a $10k truck).
 

rd3war

Member
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Location
PA
I don't think I've seen this mentioned before on here. Filling the driveshafts with expandable foam (instead of a cardboard tube) should help with small vibration issues, having them already mechanically sorted. The foam won't move around in the shaft like cardboard. It will deaden sounds and vibrations; if you hit a hollow pipe with a hammer vibration resonates through the pipe, if it is filled with foam you only get a "thud" from the hammer.
 
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