LMTV Alternator Disaster, engine now catastophic

[Awesomeness]

A few points:

1. If someone put together an "emergency" kit that included: Alt L bracket, Alt Bolts, Alt belt, Water Pump, Water pump belt, Water pump seals, Easy out, drill bit, Loctite. I would certainly buy one. Anything else that would be required to make sure you can sort out this alternator problem the first time you notice it's loose. Sounds like potentially a U as well.

2. I've read a few trucks have the fan blades go through the radiator. Would be be possible to fab a metal(steel) shield to protect the radiator from the fan?

3. Towing services. Could we put together a guide on how to get the LMTV towed and expected prices (general ideas). I personally have no idea who to contact if I break down somewhere.

4. Find a scientific way to measure the driveline vibration to meter and predict when it's doing damage?

5. Write a PMCS guide for which bolts and things to check regarding this vibration issue? I think it's in a few threads but summarizing it would be great. I've already lost the top alternator bolt twice. Fortunately they are cheap and common.

1. While the kit seems like a good idea, the "fix" is to have the driveshafts rebalanced/repaired, so unless the kit contained extra driveshafts you would likely fix the symptoms (e.g. alternator bolts, water pump stuff) and then break it again another half hour down the road.

2. Sure, pretty easy to do. Just get some expanded metal grate and make a piece that lays against the rear face of the radiator.

3. Towing these things isn't as tricky as it seems. Heavy duty towing services are everywhere, since big trucks that need recovery are everywhere. Many even offer roadside repair, including stuff like making hydraulic hoses right from the repair truck, because they are typically coming to rescue a commercial truck that is down, and the company is losing money every minute it's not driving. Also for that reason, it's pricey. Getting an FMTV towed is about $300 just for them to respond and pull the driveshaft, and then some number of dollars per mile, so get your wallet out.

4. The scientific ways to measure it are pretty straightforward, and detailed in the engineering reports the government commissioned to figure out why they were destroying drivelines. It's not really something you can just drive around with the instrumentation attached though. I think the bottom line of the story is that if you are driving along and the waterpump or alternator break, STOP, pull the driveshafts and have them balanced/straightened/repaired and/or replace the u-joints.

5. It's on my list of things to do for my "common problems" document, I just haven't got around to it yet. My guess at the sequence of events is that the driveshaft starts to experience vibration (e.g. unbalance, "hinging", wear, etc.), that vibrates the bolts out of the caps of the u-joints (because the military never seems to put the safety tab plates on, or Loctite on the bolts), this amplifies the vibration in a huge way, the amplified vibration shakes the engine significantly, stuff starts breaking on the engine (e.g. cracking water pumps, vibrating bolts out of waterpump or alternator which lets it really shake around and beat itself to death, breaking off fans and starters, breaking transmission cooler lines, etc.). If you're already losing bolts out of the alternator, my suspicion is that you're already on the path. It's probably good to take all the alternator and water pump bolts out, clean them, and [blue] Loctite them, though on the other hand they really shouldn't be vibrating out under normal conditions so maybe it's better to just leave them since they are early warning indicators? I could understand the logic of either argument (mine are currently Loctited).

 

[frank8003]

"So, now that they are new shafts there obviously ZERO lateral/ hinging movement in the splines. I took it for a test drive and it is so much nicer. There was vibrations before that are not there now. My truck had noises and vibrations from the day I got her and I knew no difference. But now I can tell that the shafts were a source because it isn't there anymore."
~" I provided him with the study report posted prior I the chain. He will read it and give me his understanding of it."~

Good story, Happy ending, Obviously you just helped all. Thanks for posting the troubles and resolutions.
I wanted to put some of that in bold or capitals but that considered inconsiderate, but Thanks.

 

[1951M1078]

Has anyone found a better system ? And / or what do I tell the drive line shop to do ?

I have mismatched tires (all different OD's and 2 different manufactures ) and the old drive shaft that was changed ( D ). And I have a vibration that sets in at about 35 mph. It comes and go's at times so I have not done much over 45 mph.Still need to do the check on the joints.

Will be going to newer tires that will be all the same and will look into doing a on truck balance.

 

[Awesomeness]

Has anyone found a better system ? And / or what do I tell the drive line shop to do ?

I have mismatched tires (all different OD's and 2 different manufactures ) and the old drive shaft that was changed ( D ). And I have a vibration that sets in at about 35 mph. It comes and go's at times so I have not done much over 45 mph.Still need to do the check on the joints.

Will be going to newer tires that will be all the same and will look into doing a on truck balance.

Just so people are aware, there are previous threads on this where it has been talked about in depth. I'm surprised longtime members are finding this information new.

The military engineering studies test other types of driveshaft and u-joint setups. They come to the conclusion / recommendation on some particular better type of driveshaft / yoke / u-joint if a couple issues (e.g. waterproofing) they had in testing can be solved. The study also recommends that a short term fix is to install heavier duty versions of the driveshaft and u-joints, to improve survivability. The Army did the latter, installing heavier duty shafts and joints on all the FMTVs, and never did anything with the design that worked better. Maybe they were never able to solve the issues, maybe they never tried, and maybe we could switch to their recommendations aftermarket with or without addressing those shortcomings.

You don't need to tell the driveshaft shop much of anything. Just taking the shaft in (with your u-joints installed) to be "balanced and straightened" is their standard work. They'll put it on a lathe-like machine, spin it, and measure the runout and balance. That service is typically around $100 per shaft, plus any other services they discover are needed (mine added $250 to replace one yoke), and around $50 per u-joint if they need replaced. Based on a few people that have taken their shafts in, expect around $500 total per shaft.

Keep in mind that engine vibrations would show up at a certain RPM (thus it will be experienced at that RPM in each gear), tire and driveshaft vibrations will show up only at certain speeds regardless of the gear the transmission is in. Like the Tacoma Narrows Bridge fluttering in the video above, "at resonant frequencies, small periodic driving forces have the ability to produce large amplitude oscillations, due to the storage of vibrational energy." In other words, tiny vibrations (e.g. driveshaft moving a few thousandths of an inch several hundred times per second) result in huge vibrations (e.g. whole 1600lb engine flopping up and down several times a second). This happens at multiplications of the resonant vibration frequency (for example 300, 600, 900, 1200 RPM) with one of them being the most destructive, but all of them showing more vibration than "normal" (other in-between frequencies, like 450, 750, etc.).

Vibrations from the tires should generally only vibrate the axles into a resonant situation, because the axles are sprung and damped (shock absorbers) from the truck. It's unlikely the axle then vibrating (bouncing up and down) would send the truck/engine into a resonant mode too. It would just shake it like you were driving on a bumpy road, which we hope the truck and engine components are generally capable of withstanding. The driveshafts however are attached right to the transmission and then engine, so any vibrations they transmit go right into the engine and can set up resonant vibration destruction there. With this in mind, we would expect that a tire vibration (if resonant) would destroy axle stuff (e.g. wheel bearings, seals, loosen bolts), while driveshaft / u-joint vibrations would shake the engine or axle pinion. Parts attached to the axle extremities (e.g. brake chambers, wheel bearings, etc.) are probably safe to assume are designed to handle quite a bit of being thrown around, since the axle is bouncing up and down constantly. Components attached to the engine (e.g. alternator, fan, water pump, etc.) were not expected to experience such violent abuse, which is probably why we see them failing first.

I hope that's not overly technical, but it's my current theory of what's happening. While I don't think tire vibrations are likely to break stuff, it's also probably smart to intentionally avoid driving at resonant tire frequencies (e.g. don't drive at 35MPH where the vibration is worst - instead go 30 or 40).

Another interesting look at how resonance affects things, that might be more familiar to members here, is chatter while machining metal parts. Haas brand lathes actually include a feature where they surge RPM (e.g. you are targeting 1000 RPM but they bounce between 950-1050 RPM) to avoid hanging out too long at a resonant frequency (that causes chatter). This video give a really good demonstration of how it helps, along with some good visual descriptions (starting around the 1m:30s mark) of chatter (resonance): https://diy.haascnc.com/videos/lathe-spindle-speed-variation-stop-chatter-during-cnc-turning

 

[aleigh]

Bet that was a nail biting game to watch in the stands!!

Ugh. We got Walshed man. I was up on the 50 and from where I was it looked good, and I recall foolishly celebrating along with everyone else in that section. The only thing that makes this feel better is the Panthers lost so it "didn't matter" but still.

To everyone going on about the driveshafts, that's interesting, but I'd like to remind everyone I've had the truck for 17,000 miles. In two years. I find it surprising it got that far just for 3 things to break within a couple hundred miles all because of drive-line vibration problems. Which also ignores the fact, as I've pointed out, that the coolant boiled, which is hard on everything, especially an old coolant system. When we pulled the alternator off it didn't have bushings pressed in (some seem to, others don't), and the holes were worn. The metal of the casing looks soft. And if you look at the design of the mount the alternator is going to be subject to vibrations. You don't have to drag the driveshaft in - I go off-roading and bang the truck all around.

So my personal belief is, the pivot bolt worked out probably with help from the fact the alternator had free space to vibrate because of tolerances between the holes and the bolt, it worked out (for not the first time - and here is my fault since I knew this was an issue), and of course it snapped. Then it boiled and weakened the water pump, which went. As for the fan well shrug it was a new unknown part. Who knows. Correlation is not causation.

The plan right now is I'll get a new pump ordered today, get the old one out and pull the radiator and see where it is damage wise, and just go from there.

I did have a guy come out and steam clean it, so at least there's that. It'll be nice to work on.

 

[Awesomeness]

To everyone going on about the driveshafts, that's interesting, but I'd like to remind everyone I've had the truck for 17,000 miles. In two years. I find it surprising it got that far just for 3 things to break within a couple hundred miles all because of drive-line vibration problems.

Isn't that how pretty much everything breaks? It was working well for a long time, then it doesn't anymore. And three seemingly unrelated things breaking at essentially the same time should send you looking for an overarching cause, or it could all just be a coincidence. That's why I went ahead and provided a more scientific explanation above. Take it if you want, and risk needlessly spending money to have the driveshafts balanced when they're fine, or don't believe it and start driving again and see if something else breaks.

For the record, I kept driving mine, and it broke the nose of the starter off and then cracked both sides of my engine block, broke a 8" piece off the top of the transmission bellhousing, in just the 30 mile drive home! So while I probably represent the worst case (and I have luck like you), it's a potential ~$10,000 mistake. If you find my original post, you'll see I had the exact same pattern of failures as you (e.g. water pump, alternator, u-joints), and it's the same as several other posts, and that described in the military engineering reports. So the "correlation is not causation" comment seems to have a lot of data to the contrary - that would have me concerned.

 

[aleigh]

I don't think that coolant boiling and blowing steam through water pump seals because the alternator dropped the water pump belt when it broke off is "unrelated". People seem to be saying that and I don't know why. The engine is designed to hold a hot fluid, not high pressure steam. It was coming out of various fittings. Frankly when we put it all back together and I drive it on a test drive and it was holding pressure at temp we were all surprised, me, the mechanics. Then a few hours later the water pump blows a seal. My surprises about this are 0.

I am not saying the driveshafts were not your cause. I am not saying that I am not going to have them spin balanced because it's cheap insurance as you point out. I am not even saying that the driveshafts are not my cause - how could I know? - I am just saying there are simpler explanations worth considering.

 

[Awesomeness]

The engine is designed to hold a hot fluid, not high pressure steam.

While I don't agree with this statement at all (the water boils because there is no pressure, or else it wouldn't boil, so there is no "high pressure steam" either), I don't think it's related. I'm not sure how closely you've read the other threads, or the military engineering reports, but it's uncanny how similar they all are (including your story).

Mine started with a leaking waterpump, which turned out to be a hairline crack. I replaced the waterpump housing, and drove, and it vibrated all the waterpump bolts out. At first I thought it was just that I installed them poorly (which I found unlikely, because I even Loctited them, but I had no other explanation at the time). Then I broke the top alternator L-bracket on the next drive, which I replaced with an unbreakable 1/2" thick one. Then I took it on one drive and broke the bottom ear off the alternator, so I just removed the alternator to get it home. On the drive back home I cracked the block and found the starter hanging by the cables. After replacing the engine (ugh), I had the front driveshaft tested and it was at 0.055" runout (acceptable is <0.005").

One of the other posts is titled something like "Help, I keep breaking water pumps and alternator brackets." The first thing that breaks in the military engineering tests is the water pump cracks after like 50 miles. The stories are so similar they really don't leave much room for any other interpretations (besides random simultaneous failure, which is an unfathomably unlikely event).

Maybe I'm just regretful that I didn't think it through in my case, and look where it got me. All the signs were there, even if I didn't know about the other cases. Once I learned about everything else, I felt really foolish. I just want others to have the maximum opportunity to not make the same mistakes I did (or that others did, according to their stories).

 

[aleigh]

That's fair. And I do appreciate everyone's feedback.

You're right about the cooling system holding working pressure - I did not communicate clearly I meant is that it it was clearly OVER pressure. Steam was blowing out of coolant lines, the screw fittings, everything. It looked like a cartoon of a steam engine. Frankly if the engine is working in another 5,000 miles I'll be surprised I didn't cook a head gasket or warp something.

I am asking myself questions like why didn't my radiator cap vent the pressure (or enough of the pressure). I hear your regret and I take the driveshaft issue seriously. But there are other factors too. Like I recently changed to XML tires and they are less balanced and have more road vibration than my previous MVTs did. And there is the fact I use this truck off-road, so I need it to withstand vibrations.

I do diagnostics of technical systems for a living and my reaction is just you can't assume anything. All this information gives really good places to look but we can't rush for a complex explanation when there are simpler solutions. I don't even know if my motor mounts are in good condition for example.

 

[aleigh]

On a tangent, I am glad I left the M1082 in PHX. One of the points of this trip was to bring a load of cargo back to PHX and I could have gotten it all with one trip using the trailer, but I thought eh, maybe not so much since since it was new to me.

 

[Awesomeness]

When I blew the water pump it looked the same. Coolant and steam spraying everywhere. I did address the other factors (e.g. off road use, tire vibrations) in my explanation, and I offroad mine too. I'm seeing these as more similar than dissimilar (same goes for the other stories, and the military reports).

Considering the potentially damaging and expensive chain of events, I'm basically saying that "If you break the water pump or alternator, the next immediate step is to pull the driveshafts and u-joints and have them checked and repaired." That's if just one happened. If there are issues with more of these (e.g. alternator mounts, water pump, u-joints, cracked oil cooler hard lines, broken fan blades, broken alternator mounts, broken air compressor mounts... essentially "extremity engine accessories") you are drastically increasing the likelihood that the known driveshaft issues are the problem too.

At least in the process of writing all these posts I've generated most of the content I need my common break/fix document.

 

[aleigh]

Funny enough now that you mention that I did crack a oil cooler hard line a long time ago. Not long after I got it.

You obviously have taken this issue to heart, and I don't blame you, so I wonder have you looked into putting a vibration gauge on the engine? Because I am kind of at that point, to get data.

 

[coachgeo]

FWIW if anyone cares; the type joints recommended by the study to use with driveshafts to highly reduce vibration issues transferred via driveshafts, was Rzeppa style joint(s), but then again that refereed mostly to rear shaft studied which has steepest angle. Thus the Double Cardan type may be just fine for the front... Choose your Poison I guess.

 

[aleigh]

Would a mod please change the title to "LMTV Alternator Disaster" or something similar. I don't want people to get the impression I currently broken down and need help. I hunted around for a way to edit it myself but it didn't seem possible.

 

[coachgeo]

Would a mod please change the title to "LMTV Alternator Disaster" or something similar. I don't want people to get the impression I currently broken down and need help. I hunted around for a way to edit it myself but it didn't seem possible.

You'll need to PM a moderator. Odd's are they will never see this post with out a PM. You are right that only they or Admin. can change thread titles. Common way it is on Bulletin Boards.

 

[aleigh]

You'll need to PM a moderator. Odd's are they will never see this post with out a PM. You are right that only they or Admin. can change thread titles. Common way it is on Bulletin Boards.

Wilco!

I just realized, I need the truck back by 1/28 for the show in Phoenix!

 

[coachgeo]

Wilco!....

IMHO just have them put a big WAS!! in front of your thread title so it addresses your first post about being broke down. If it is still editable. you might want to put an "UPDATE: no longer stranded" or something like that inside your opening Post as well. Even Mods can not edit them once they are automatically closed for archiving.

 

[Adventure Driven]

yea I just read your thread, a huge bummer, man I wish we could figure out what the heck makes this happen, I am stumped

Seth

Would a mod please change the title to "LMTV Alternator Disaster" or something similar. I don't want people to get the impression I currently broken down and need help. I hunted around for a way to edit it myself but it didn't seem possible.

 

[Awesomeness]

If you have just one component fail (e.g. cooler hard line), it's probably a smaller chance that it's a driveline vibration. Just making up numbers, I'm thinking like 25% chance. But if you fix it and "immediately" (within 50 miles) break another item on the list, I think that chance just jumped significantly (80%). If you're then at 3+ broken components, it's almost certain. However, even if just one breaks, and especially if it's the water pump or alternator which seem to fail first in almost all stories, the likelihood of issues in the very near future (e.g. on the drive back home) is high enough (25%) to have the driveshafts checked. Of course some logic should be used as to exactly what broke and how it failed... if a transmission hard line broke after it has been rubbing against something, or the water pump is leaking out the seal on the shaft, that's probably obviously not related, but if the water pump housing cracks or you break the ear off the alternator, those are pretty clear violent mechanical failures.

I haven't really considered using instruments to gather more vibration data. I've fixed most everything on mine now, so I'm not sure what I would find, except control data. I think if you break one "extremity engine accessory", have the driveshafts checked, and they are out of balance/runout, you've emperically found the problem. If you break multiple things and find that the driveshafts are good, that would be the real puzzler. It's unfortunate there isn't a good way to perform a driveshaft balance / runout test in the field, besides to wiggle it and look for the presence of play.

I've taken it to heart, partly because it cost me as much as the original purchase price of the truck to fix (and it was a huge pain to change the engine and everything), but also partly because I'm a mechanical engineer and figuring out problems like this really bothers me. I hate when things break, and I really hate when there is no good explanation.

 

[Awesomeness]

FWIW if anyone cares; the type joints recommended by the study to use with driveshafts to highly reduce vibration issues transferred via driveshafts, was Rzeppa style joint(s), but then again that refereed mostly to rear shaft studied which has steepest angle. Thus the Double Cardan type may be just fine for the front... Choose your Poison I guess.

When I originally read the military engineering reports, I looked those up. They're the style on a lot of Toyotas, and would require new yokes installed on the transfer case and axles, I think.