Unknown noise from rear end on '97 Z3 2.8 5-sp

[johnnyo55]

Hello to all. Recently I've been hearing a VERY high frequency, "squeaking" noise that seems to be coming from the rear end. This noise is most pronounced when I let off the throttle, and seems to disappear when the throttle is back "on". It also is most pronounced when the car is "cold", and diminishes somewhat after the car has been driven for a bit. Any ideas as to what this might be?

[zellamay]

Diff oil? How much is in there and what does it look like? Even when the oil has seemed okay, I have had success with upgrading it. But... the "high frequency makes me wonder if it's something else. I'd look around for rubbing/ banging parts also. The "cold" part could be the diff, or it could be exhaust parts expanding with heat just enough to touch something.

[johnnyo55]

My mech seems to think that it may be exhaust related as well. I (myself) changed it out for an Italian stainless system with a much better sound several years ago; perhaps the mounting bolts have loosened enough by now to allow this noise to happen. I'm hoping it's that simple! Got to put her up in the air to figure it out. I'm hoping it's not the diff self-destructing...