Boxerworks.com

Not sure what the deal was, but some of the rear drives I've pulled off had a bendable lock washer under that nut, some have not. Is it something BMW added later to deal with the loosening nuts? If you just need to tighten that nut, strap the rear drive to your wheel to keep it from turning, and torque away.

I called Alamo BMW to see about tightening it and the GREDDY #$@holes want 100 bucks. I ordered the tool from Cycle Works to do it myself. Snowbum says put blue locktite to keep it from coming loose which is what I'm going to do.