FWIW, ask what they mean by rebuilding - if it is just cleaning, regreasing and rebooting, it is a pretty easy DIY. Certainly no harder than getting the axle out if you are willing to do that. Replace the e-torx-head bolts on the differential while you are doing all this, too.

There are several YouTube videos that show the process - nothing particularly hard. I had always avoided it, but didn't feel like laying out 2x$550 for new dealer rear axles when the boots went south, so BMW sort of forced my hand and it turned out to be pretty easy. But only for those not ashamed to be covered elbow-deep in CV grease...

It's been a year, so I guess it worked. For the heck of it, I used Redline's synthetic CV grease - very gooey, high-melting stuff.

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David.X5
2001 X5 4.4i Sport
SOLD! at 160k miles