I have a 2000 Blazer 4DR that now has a whistle coming from the differential. It was low on fluid when the sound started. It is intermittent depending on slow speed and decelerating. It is not a gear grinding noise, but a resonating whistle. Is this a ring gear or a pilot bearing sound possibly? Any cures?

 

You most likely have a bearing starting to go in the rear end. I would recommend dropping the cover and having a look at the conditions of the gears and feel for any play in the bearings. You may need to disconnect the driveshaft from the rear end to feel for play in the pinion bearings.

 

The noise is coming from the pinion bearing location but I could see no gear wear or shaft play. I have a couple questions about replacing the bearings.
1. Is it possible to remove the bearing races without removing the collapsible spacer? Can they be pounded out, or is there no clearance for a drive tool with the spacer still inserted?
2. If I have to remove and replace the spacer, what kind of torque is needed to compress a new one? I have a standard Chicago Pneumatic 1 /2" air gun at 120 PSI.
3. Can the spacer be compressed with the pinion itself? I don't have access to the GM tool that is normally used?

 

I didn't have any problems getting it apart as I thought I would. The replacement was obvious once I had the pinion knocked out. There was a glazed area on the front bearing race that I an guessing is what caused the whine.
Thanks

 

I replaced the bearing and it didn't help. Apparently the ring gear must have warped when low on fluid. Looks fine - but no good.

I replaced the axle with a used one from a salvage yard.