This is right down my alley! Mine made noise from the beginning, which was on the highway driving to the race track. After racing and not breaking it I decided it could wait until later. When they originally opened my differential it was almost dry which left me wondering if the noise was the bearings but over time it became clear that it was both. Fast forward to the present. I bought new side bearings, seals and a selection of shims and took it back to the shop. The contact pattern on the gears was too deep in the grooves. They adjusted the meshing with the shims I purchased and replaced the bearings. I still have a bearing noise but the whine is gone. When they opened it up it was full and clean. I'm using Motul 75-140 competition oil in mine now. The bearing noise I still have will be tracked down soon. I just hope it's not the pinion bearing.

Les