As I mentioned above.

The 2004 X3 2.5i with 100K miles...
I replaced the rear u-joint for $20...
Also installed new Giubo (SGF) and CSB (BMW Genuine part).
All is good now.

The key thing: use washers to gauge the depth of insertion of the u-joint in the yoke ear.
I rented a ball joint tool from Advanced Auto and used the big C-Clamp to press the old u-joint out.
Then new u-joint goes in and restaked it.

I can do a writeup later...

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1998 E39 528i 5sp MT
2006 E53 X5 3.0 6sp MT