Dude you totally scared me resurrecting this thread!

I should update, though - that sound finally went away for me. My post above (#32) said that it came back even after the rear diff rebuild and new tires. Well it did, but just a couple of times, and it's been silent ever since.

Btw, my problem was not the one described by t2p in post #37 - my screech sound was definitely coming from the back end.