slather some very good CV joint on the splines and work them in the spline grooves.

My W124 had this problem and I got some proper CVJ grease with extra moly compound in it when I redid the centre bearing. It was smooth rolling again.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)