I had 2 different gear set installed with new pinion bearings and both had the bearing fail. I am fighting this with my credit card company. When a second shop opened the rear the bearing was in pieces. they sent a letter to the CC stating they found "excessive backlash causing the pinion bearing to come apart". CC is arguing that the second shop didnt say it was caused by a bad installation.

 

notice the damage to the posi and ring gear tooth from bearing.

http://images2d.snapfish.com/2323232...3B332%3Cnu0mrj

parts the magnet picked up at 500 miles. to bad it didnt pick up the loose bearings floating around.

http://images2c.snapfish.com/2323232...982%3B58nu0mrj

 

If the pinion bearing(s) were the first to fail:

1) improperly installed crush sleeve (under or over torque can cause excessive bearing movement; without the correct preload, the pinion would 'walk' back and forth)

2) improper pinion depth (the clearance between the gears would be off)

3) using grease on the bearings during install (do this doesn't allow the gear oil to penetrate the bearings during normal use)

4) Insufficient break-in period (the first 50 miles are crucial to prevent from overheating the gear set) {I suppose that heat could also be transferred to the bearings}

5) reuse of the old races (with new bearings- new races are required to work correctly)


UPDATE: from the pictures, I would think 1 or 2 would be the cause. that damage to the diff. housing is really severe.

 

Def improper installation.

How can the CC say that "excessive backlash causing the pinion bearing to come apart" doesnt have anything to do with install. It has EVERYTHING to do with install. I would have the shop re-write the info for the CC so that they can understand that it does have to do with the install. I wouldnt change what they say but at least have them explain what they mean.

 

They reused the crush sleeve and didnt install a new one as it requires.
Thats my take on the failure....
Or improper synthetic lube levels.