London_V do you still have this noise?
The dust covers in question (IF that is what is making this noise) sit on the inboard sides of the rear driveshafts, the shafts that go from the rear differential to the wheels. The dust covers protect the shaft seals of the differential.
My car has this noise coming from the rear, had it for ages. It's been into the local BMW dealer, and they have diagnosed it as these covers being the problem.
https://www.newtis.info/tisv2/a/en/g...aft/1VncI9NLKc
That's the link for the workshop manual, there is a lot involved to change these dust covers.
I haven't had mine changed yet, hopefully can get it booked in soon.