something getting loose in the drivetrain

[Rawze]

(02-26-2018 )the missing link Wrote:  Yes the international were horribly for the damm u- bolts backing off , most of the time you can see them working back and forth
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If your referring to the u-bolts that hold the rear axle to the springs on the prostars then the u-bolts are not the actual problem. I faced this same issue with my prostar when the truck was brand new.

- The actual problem is that the carrier block that mates directly to the spring is not ground properly.

- hundreds and hundreds of pro-stars had this problem and it is so bad, you can spot it just by looking at one. The outer leaf will not be aligned to the inner one at the front of the leaf spring after they have slipped. It causes alignment issues and most mechaincs blamed it on weak and/or under-torqued u-bolts. The problem is that you can tighten the crap out of them (they are only supposed to be torqued at 600 ft-lbs max), but they keep slipping. Some shops would over-tighten them, but there has been more than a few prostars where that was done, and it caused a u-bolt failure and a wreck.

- I spoke to Eaton about this back in 2011 when mine was having this issue. They had no real answer but told me that a company in china made the components. I called a company called "Koman" over in china (yes I really did that) and found out from the guys there that it is a mis-matched carrier block. The correct solution is to remove it and re-grind it to the same curve as the spring so that it has 100% contact area and the problem would be solved. We took ours apart and this is what we found...

(Wife helping me remove carrier rear axle blocks back in 2011 when we first got our truck)...
   

(here is the actual problem).
   
In the pic above, the entire surface should have been shiny due to slippage, but as you can see, less than half the surface area was making contact under full torque of the u-bolts.

- It took us about a day or so to sand them and grind them to a matching fit. We re-installed them and torqued them to 600-ft lbs like recommended. -- To this day, we have had ZERO alignment issues or slippage problems at all. There is more than a million miles on the rears now at this joint, problem free.

- During the conversation, it was also mentioned that the blocks are supposed to be friction fitted to 100% contact area and that they should be placed so that the pins are at the center of the slot on all 4 blocks. DO NOT use the slots in the blocks for axle aliment purposes, keep them centered when installing the axles to the springs. The torque of the u-bolts is also critical for a proper allowance of "slip" for those moments when a driver slams the truck into a trailer quite hard. -- I.E., when it is set properly and there is 100% contact area like it should be, there is enough pressure for it not to slip except under extreme conditions. The slots in the block are actually for slippage (all 4 blocks = 4" of travel) if someone slams the truck into a hard stop in reverse to prevent the diff teeth from getting broken. if this happens, then the u-bolts should be replaced and the blocks set back to their center point.

In other words,.. YES, it is designed to move,... BUT it is NOT supposed to unless someone abuses the truck badly. -- the problem is that many hundreds of rears ended up on prostars without these blocks ground properly by International/Eaton when assembled.

We solved our years ago and i have seen countless prostars with this problem. There is a proper solution and it is NOT by tightening the u-bolts to the breaking/danger point. I was told of one driver that got killed because his rear axle tires "kissed" each other at highway speed after someone over-tightened these u-bolts, resulting in their failure because they could not get the rears to stop moving around.