One of our customers had a loud diff in his Q4. I installed a good LSD used unit we had in stock 4k mi. into a 2018 Q4 with over 60k mi. Jet black oil came out, and that was after an oil change around 50K. After swap I dismantled the old diff to inspect the whining/growl it had. R&P had a bad pattern( hard to say if set up was bad or the LSD clutch material contaminating the oil caused it), bearings seemed fine. The clutch pack definitely had wear, I think it was stacked wrong from the get go. One clutch was against the sun gear cup directly. Swapping out third member is not to bad overall.
Alfa Parts Exchange
Alfa Parts Exchange