My new LMTV is blowing water pumps and loosing alternator brackets!

[coachgeo]

It looks like that is the later (2003) study. Here's the first one (1998 ).....

Thanks for posting this. You are correct was thinking of the 2003 study.

Sounds like need to look at a way to get more weight carried by other places to lesson it some on the Water pump since some in here are still having issues.

Can we get folk to post pictures of their brackets? Maybe the folk who have had problems did not get on their truck an updated bracket?


this study interestingly said the larger rear driveline (4") would work as a delay in damages but not stop it when it comes to the Bell Housing and the Tcase Housing. VERY INTERESTING. Must be why the low tolerances of play got put into the TM's. Interesting that they stayed with that route up untill 2008 instead of swapping to the suggested driveshaft change the 2003 study recommended.

98 study also suggest the use of the 6x6 axle but possibly with different angles built into various mounts. (engine and tranny mounts) Hmmm.... though it was noted that suggested angles changed would improve rear driveline issues..... doing so would negatively effect front driveshaft angles thus potentially cause issues there.

Soooooo what "all" did they do when they built the A1P2's with the 6x6 axle???? (power divider Box axle) hmmmm...??? Anyone got any connections with folk who may know more about this?

​Thanks again for digging out this info.

 

[Duckworthe]

So I took my truck into my buddies driveline shop here in San Diego he also works on many military trucks contracted through the Gov.. He looked at my shafts and said "Eric, your u joints appear to be fine, however the slip joints are shot." I told him that the manual has allowance for .005 hinging. He laughed at that and said "sure if you want to risk blowing your driveline. That is an allowance put in place to basically allow these trucks to keep moving or (be allowable to drive". My truck now has 20,000 miles on it. And his words were more like 120,000 by the spline wear. He said either buy new or rebuild them. I chose to rebuild them as I don't know what I am really going to get buying someone's parts. If I had to pay for the labor and parts it would be $500.00 per shaft. I only have to pay for parts so its about 175.00 per shaft. Unless a u-joint needs replaced also. He said that there should be NO, as in zero, hinging movement in the shaft. As for the drive line angles, he said that will wear out u joints faster but not the splines. His quote to share was "If you want to risk blowing a driveshaft and transfer case, and further possible damage, go with the .005 hinge plan. But that is just for moving the truck around some. Not travelling down the highway going to the desert for the weekend." So I am pulling my shafts today and having him rebuild, dynamically balance them, and give them back to me 100% ready to go. I can't risk the possible damage to major components. I provided him with the study report posted prior I the chain. He will read it and give me his understanding of it. Todd has been building Drivelines for cars through semi trucks for over 45 years. He has built all of my off-road race truck and circle track shafts for about 20 years, so I trust his assessment and knowledge. I will get them back after thanksgiving and will reinstall them followed by a report of any truck characteristic changes. I hope this helps some of you out there. My bottom line is this. $1000.00 vs. a transfer case or more is money well spent!

 

[Suprman]

I thought it was .0015 allowed play. The local units here cut that in half. And if you do chuck a driveshaft and it shatters your transfer case, it usually causes hairline cracks in the transmission casing also.

 

[Awesomeness]

In reading the studies, it talks about how they put new tight and balanced shafts on, and the truck promptly destroys them. I think it was within 100 miles of driving, and they are back to like 0.015" hinging. Then, the study points out that it didn't degrade much worse from there, regardless of time in service.

 

[coachgeo]

.... I told him that the manual has allowance for .005 hinging. He laughed at that and said "sure if you want to risk blowing your driveline. That is an allowance put in place to basically allow these trucks to keep moving or (be allowable to drive". ....He said that there should be NO, as in zero, hinging movement in the shaft. As for the drive line angles, he said that will wear out u joints faster but not the splines. His quote to share was "If you want to risk blowing a driveshaft and transfer case, and further possible damage, go with the .005 hinge plan. But that is just for moving the truck around some. Not travelling down the highway going to the desert for the weekend." ....

Confused..... thought that it was posted earlier that the .005 (or .0015 whichever it is) was even more strict "time to replace" measure than an average hinge test specification. If you get a chance...... can you ask you guy what the typical commercial Trucks hinge test specification is? Would make an interesting comparison.

Moderator...... we are getting off on a tangent of this thread. Might be wise to split the deeper dive into driveshaft stuff off into it's own thread..

 

[coachgeo]

In reading the studies, it talks about how they put new tight and balanced shafts on, and the truck promptly destroys them. I think it was within 100 miles of driving, and they are back to like 0.015" hinging. Then, the study points out that it didn't degrade much worse from there, regardless of time in service.

And if recall right it noted that the damage seemed to happen off road most due to greater articulation of the rear suspension. Sorta opposite of what this fellow says though. grrr. confusing.

 

[Awesomeness]

The damage in the test occurred in the on-road test, I believe. Reading the whole test is pretty interesting... what a cluster-frack. They pretty much destroy the driveline and a couple engines and transmissions within a couple thousand miles, and it doesn't even look like they set up any especially harsh conditions. They just put it on the dyno and drive, and break things.

The off-road jouncing tests show that the problems they experienced would worsen off-road, as the forces rise drastically.

Michigan Scientific delivered a modified driveshaft that was stiffened to reduce, and hopefully eliminate, the hinging effects (see figure 10). Hinging is what occurs when the two ends of the driveshaft bend in opposite directions. It is determined by the distance between the spline contacts. As seen in figure 10, the shaft has a tube over both sections, welded to the long with a tight fit on the short end. This keeps the shaft from hinging in the spline.

...

The data for both the MSC driveshaft and the production driveshaft indicated marked increase in acceleration levels as the driveline angle increased. The MSC driveshaft, with the elimination of the hinging effect, proved more effective than the production driveshaft with nylon thrust washers in the resonant frequency range at the high angles. Outside of the resonant range and high angles, no particular driveshaft had an advantage all the time.

...

When the new Al shafts and full round yokes arrived they were immediately installed on the vehicle. An Al shaft is 4 inches in diameter, has a longer spline engagement, and is more precisely balanced. The accompanying yokes are full round, meaning they no longer require straps to bolt the driveshaft in place. Since time was a constraint these shafts were not sent out to have the balance and straightness checked.

...

The 6000 mile durability test was re-started. The hinging was recorded to be 0.010 inches. After 173 miles of running the hinging had increased to 0.015 inches.

...

Because of our recorded increase in hinging, Meritor came out to perform a hinging measurement on the rear driveshaft and see if it was still in good shape. The hinging value came in between 0.011 inches and 0.012 inches. Heat does not affect the hinging measurements so we must have been doing our measurements inaccurately.

...

The vehicle had completed 1382 miles of durability testing. The driveshaft and the flywheel housing had not failed and were performing successfully at this point.

...

A final hinging measurement showed a maximum hinging of 0.0155 inches. Meritor did not check the hinging for us this time. Keeping with just the hinging number we measured then, over the 1382 miles the driveshaft hinging rapidly increased 0.005 inches but then only increased 0.0005 inches for the remainder of the test.

 

[Duckworthe]

If you get a chance...... can you ask you guy what the typical commercial Trucks hinge test specification is? Would make an interesting comparison.


I dropped my shafts off yesterday to get rebuilt. Shaft came out easy, but boy are they heavy, especially the rear. I will have better then new shafts and joints when returned. I did ask him about the commercial trucks tolerances. In civilian world they don't call it a hinge test or hinge movement, its called Lateral spline movement. His answer was, quote "zero, if it has lateral spline movement it needs to be replaced." end quote. Again my truck has 20,000 miles on it now and he said it looks like 120,000! the only real thing wrong with my u-joints was the cap seals were dried out. So I am just starting totally new on these items. Probably wont get them back till after Thanksgiving as he is booked up with paying customers. But I will post what I find after rebuild and reinstall.
I forgot to mention that he stated that, quote "with ANY lateral movement the test stand will reject the shaft and stop the test. The reason that lateral spline movement is so bad is every time the shaft turns it drops however many .0001 it is off. this Dropping effect is basically where most of the vibration will come from and it turns into a pounding/shaft dropping force that will beat the shaft apart and or push driveline vibration to other areas of the truck. Since our trucks have automatics the end results are far worst and devastating. On a manual trans you might not notice it as much because of the huge and heavy gears that can take more forces placed on them then an auto can take through its small trust washers." end quote. He also stated that he sees trucks with far worst driveline angles everyday. Our trucks angles are nothing and my joints are in amazing shape minus the dry cap seals.
Thanks,
Eric

 

[Awesomeness]

Thanks, it will be interesting to see how far out of spec your shafts were.

 

[f8617]

Looking at the diagram it looks like the water pump mates to the block using a round o-ring and has 2 hoses coming out of it that also use o-rings. I was assuming the pump mated using a flat gasket like on a gas car.

No gasket, just o-rings (see pix, H2O pump).
Also, after replacing a H2O pump, I concluded the number of alternator & H2O pump bracket bolts to be overkill...suggesting (posted problem) was improper bolts or torque.

 

[Awesomeness]

The gasket I blew is between the two halves of the water pump (which you have assembled in your picture).

 

[Aernan]

So did another 100 mile trip in the truck and lost the same bolt. M8 1.25 x 40. I'm had a spare and put it in when I got home. I'm going to go measure the hole because I think the bolt is actually not big enough (slop in the hole). Has anyone else find a bigger bolt that fits?

 

[coachgeo]

So did another 100 mile trip in the truck and lost the same bolt. M8 1.25 x 40. I'm had a spare and put it in when I got home. I'm going to go measure the hole because I think the bolt is actually not big enough (slop in the hole). Has anyone else find a bigger bolt that fits?

Maybe it needs a helicoil; or some newer version of them, to give it better threads?

 

[Aernan]

Maybe it needs a helicoil; or some newer version of them, to give it better threads?

On mine it's the generator ear then a L bracket. Bolt goes straight through to a lock nut. I'll get a photo next time.

 

[Awesomeness]

On mine it's the generator ear then a L bracket. Bolt goes straight through to a lock nut. I'll get a photo next time.

Mine is the same. Bolt head, top alternator ear, L-bracket, locknut.

 

[coachgeo]

Mine is the same. Bolt head, top alternator ear, L-bracket, locknut.

Is lock nut welded to the bracket or? If not maybe a longer bolt and double nut? Second one a crown nut maybe?

 

[Awesomeness]

No, nothing welded to the L-bracket.

 

[Aernan]

Possible good long term solutions.
1. bigger bolt so less slop
2. use a nord lock washer to avoid vibrating the fastener appart
3. use a castle nut or safety wire
4. modify/replace L bracket with 2 ears or a stop so it rests under compression
5. figure out why the engine is shaking so much and fix it

I know option 5 is the real solution but I'm busy fixing other stuff on the truck so I will get around to it when I get there. I suspect that the engine might need a tune up (valve adjustment, fuel injection sync) and it could possibly be other root causes.

Since the bolt only costs $1.40 and it's easy to replace and causes no damage (so far) it's on my list of things I can ignore for a bit.

 

[Awesomeness]

Since the bolt only costs $1.40 and it's easy to replace and causes no damage (so far) it's on my list of things I can ignore for a bit.

The damage is that you'll just break something else. I did what you're doing, and put a grade-8 3/8" bolt in there... then promptly broke the L-bracket. I made a beefy L-bracket to replace it, 3/8" thick, and then broke the rear ear off the alternator. So it's a dangerous road you're going down - it broke for a reason, fix that reason, not the symptoms, or you'll end up with far worse problems.

 

[Aernan]

yeah agreed. I need to find the root cause.