Hi, just wanted to pipe in. Last tome I was in this thread was over a year ago but it’s been a slow year. I’m about 37k miles deeper into my X5, sitting at a few hundred over 279. My diff is TOTSLLY fine. I beat on this thing off road too. I believe my driveline noise is actually my trans, possibly a tiny bit low on fluid, and it’s been like that since about 235k miles. When i do my big suspension service I’ll also service my trans again and make sure I have enough fluid to maybe make it a little happier, lol.

If you really have diff whine, 100% start with fluid. If it keeps making noises change the fluid again to inspect and send it out for analysis.

Best of luck!

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'10 X5 35d- 279k mi, deleted and DUDMD stage 2, daily and tow vehicle
'01 330i- Drift car: SLR Super angle, BC coils- keep it simple
'07 335i 6mt - Sold @ 171k miles- stage 2 daily commuter for 2 years