Hey guys, maybe you can help....
I have a m6 car with 70k miles on it and it makes a wierd noise while driving. The best way to describe it is it is a high pitched hissing/slight whining noise that starts at 35 mph and gets progressively louder the faster you go. It is loud enough that it bounces off of other cars, the freeway wals, etc, to the point that it overpowers the noise of my exhaust. I have changed the rear fluid, and it looks like the cone clutches in the diff are cracked and broken, and I found a good deal of metal in the fluid. What would cause this noise? I have heard bad bearings, worn diffs, and this sounds nothing like any of these.

Scratching-my-head-in-Michigan...