I have just pulled my stock auburn diff - I knew the posi unit was bad because I do countless donuts and on right hand turns I could only get one wheel peel. Also about 5000 miles back lost it in a relatively sharp turn at about 50 mph and cracked a rim on a curb. Evidently this is bad for the diff bearings. About 2500 miles after my curb incident my diff started to roar like crazy from 10 mph on up - And I mean LOUD essentially undrivable. After I got the diff out, the bearing that was on the impact side showed pretty significant wear.
Anyhow I had bought a zexel diff a couple of years ago and will be attempting do swap out only the diff meaning reusing the stock gears. I will not touch the pinion gear. My question is if I reuse the stock shims (one per side) what are my chances at getting the gear setup right. And if I do have to adjust the backlash what tips do you all have. By the way when folks say they get whine after doing their own gears, is that so terrible - does whine mean destroyed gears or is it just a little annoying. I will have access to a dial indicator with magnet but I have never used one.
Any tips or suggestions will help
Thanx

 

You have a chance of getting it right, but all measurements are necessary any time it is taken apart. Ring and pinion gears come as a matched set, so you definitely (unless blind luck) will not be exactly the same as it was before.

Typically, whine means the gears are not meshing correctly. It is not just annoying, but will usually cause an irreparable wear pattern.