Twice now.
I decided to put a fresh set of 4.11 gears in my Moser 12 bolt thats in the T/A as they were getting more noisy since the whole thing was new in 2001. I bought some Motive gears from Summitt (MGR-G888411) and had a highly recomended shop do the work. He followed the recomended break-in procedure while the car was in the air and I did the recomeded word of mouth short trip easy driving for about 200 miles. Then one day I finally got on it from a 5-10 MPH roll untill I shifted to 3rd (M6) and then let up after a second or two. On decel there was bad gear whine of two different pitches winding down all the way till I stopped. Hardly noticable on drive, very loud on coast.

So I bought another set of the same gears and worked a deal with the installer to use his shop and I did most of the work and checked all the install specs. The only thing I didn't have was a pinion depth tool but I even aquired the proper inch-pound wrench to check the preload on the pinion where the mechanic just went by feel the first time. This time we also replaced the larger pinion bearing since it is r & r'd in the process, it looked fine but just wanted to eliminate any question. We did move the pinion .002 as the pattern indicated it. We ended up with a TEXTBOOK pattern and set the backlash dead center within specs. Again all the breakin proceedures where followed.

These gears were at least if not quieter than when I recieved the whole thing new from Moser with just the slightest whine at highway speed, I was very happy with this set up especially since I did most of the work and checked all the specs myself.

Then I got on it and the same *%@^!!! thing happened again!

What is the deal? Are these gears soft? I find it very hard to beleive it has anything to do with the set up or the break in.

 

Did you repalce any other bearings? Maybe one wasnt seated all the way and when you got on it it moved. Recheck your backlash. Was the carrier in tight? If not it could of moved. Did you use a new crush sleeve or the old one? I would recheck the backlash and see where its at.

 

Only the one bearing was replaced, they all looked great. The carrier was nice and tight requiring a pry bar to remove and hammer to tap back in upon installation. I have not torn it back down yet, there was nothing obvious about the last tear down with the same situation. A new GM crush sleeve was used.

When this happened with the first set Motive gears I tore it completely down and reinstalled with a new crush sleve all within specs hoping to salvage the gears but it was still as noisy as before tear down. I did run it after that and the noise did not get any worse but I decided to buy new gears and start over, hence the second paragraph of my first post.