I haven't been able to keep my 3.91s quiet for more than 1,500 miles or so for years. I just replaced a set of noisy 3.91s that had about 3,500 miles on them. I have put up with the whine for a couple of years, but it finally got to the point that I pulled them. U.S. Gears were in it before. The good Dr sent me a set of Motives this time.
We'll see how they do. I just got them in last week and have less than 100 miles on them so far.
Ever try 85w-140 gear oil?
Interesting. I have a Dr. Diff-built chunk with 3.91's in it, probably Motive. If there's any whine at all, I can't hear it over the headers and 3" (to the bumper) exhaust.
But I only have 90 miles on it so far. And I put in 85W-140 with the pouch of additive that he included in the package.
