Rear Diff Moaning

I have an `02 Rendezvous AWD w/98,000 miles that is making a moaning sound from the rear when turning. I thought(hoped) it was a wheel bearing but I'm afraid it's coming from the rear diff. To isolate the noise I disconnected the wires that go to the diff and the noise went away. I've read on some older topics and other forums that changing the expensive Versatrak fluid or even adding a few ounces of Lucas Oil Stabilizer will fix the problem. Anyone here had to deal with this recently? Thanks for any help!

There is a TSB related to this, includes changing the fluid at least 2x if I remember, then if the noise persists the diff has to be replaced, there is no field repair.