Brought my truck in because I recently rebuilt my 9" and was concerned, as I knew I set the carrier bearings up wrong. When I brought it in, the owner talked me out of working on it, on account that there was no noise. Ended up going back because I had an axle seal let go and while the axles were pulled, I figure might as well double check everything on the inside.
This is when the problems started. Right away, I started to hear some whirring/whining which got worse by the time I got home. The owner was nice enough to have me come back after hours to take a ride. His diagnosis was it was the transmission. To double check this, I found a nice hill by me, shifted the transfer case into neutral and held the clutch in to make sure the trans had 0 rpm. Even though the diagnosis was transmission, the sound was still there.
Eventually, since the only difference between the owner rebuilding it and me rebuilding was the crush collar, I pulled the pinion out to investigate. The pinion bearings did not look only 1,000 miles old. They were pitted and looked like someone took scotch brite to them (this though could be from the break-in of the new gears). So I replaced the bearings and cones and went with a solid spacer again. I ended up with a stack height of .492" vs. the crush collar that I pulled out which was .484". When I called the owner to discuss, he tried to explain that this is normal as bearings aren't always the same. While true, no bearing manufacturer is going to have +/- 0.005" tolerances. Further, because crush collars are physically crushed, they will have some elasticity which will spring the collar back slightly to a larger height. But this is not what I saw. I saw the solid spacer stack height being taller. Moreover, .484" is the size quoted for most 8.8/9" crush collars. While the owner measured .505" on the one he had (I measured the same from my Motive kit), it would be impossible to have something smaller, especially by this amount. No bearing manufacturer is going to produce bearings at these tolerances to allow this situation.
Regardless, my noise level did drop but is not completely gone. Most likely when the preload was obtained, the collar wasn't crushed. Instead the tightness of the nut was controlling the preload and most likely loosened a hair to cause my problems (can't be torqued fully). So chances are my new ring and pinion probably is toast from this as well. It also didn't help that I had an extra quart of fluid as well, which doesn't help (more fluid creates more heat as the ring gear sloshes it more).
So while the owner is knowledgeable and will try to make things right, he has a problem in admitting fault, even with all these facts. Next time around, I'll do it myself, even if I screw up as at least I make it quiet.
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