A bit late to the angel eye party: 2001 M5

[Beej]

Been into a few... did the noise come on after the fluid change?

Nope. I didn't include this info because it didn't seem useful, but...had the car for a couple months, and put the front end on jackstands for a week to do a bunch of little stuff - nothing drivetrain related. Put it on the ground and went to run some errands one morning and noticed the sound. Hadn't noticed it before, but it was different enough (and a wheel spacer caused a vibration until I later knocked some rust off the hub, just another reason to be weirded out) that I turned around and took the M3 out. Now I had spent 95% of the time before that with the windows opens, so I may not have noticed it. But even if it just started then, I can't imagine I did anything to cause it.

It's just been in the last couple weeks that I switched out the fluid (Redline MTF to BMW OE) and motor/trans mounts. It seemed like the right amount of fluid came out; I did see one tiny metal flake, but my oil catcher thing is old and there's no telling if it's from the car or some random dremel job I did in that corner of the garage. The noise didn't change afterwards.