[ALXLR]

At last the rear end noises have caught up with my 2004 XLR. After reading all of the threads I scheduled an appointmentment to have the rearend fluid changed to synthetic fluid and additive as recommended by GM. While the mechanic was under the car he noticed one of the differential axle seals leaking. Further investigation lead to the differential vent being plugged probably causing the seal to leak.
Allen

 

[Caly]

The leak seems pretty common with this differential. We had our fluid changed for the "Clunk" noise. A couple of months ago we developed a whine, for which they replaced the whole rear-end (tried to fix it and couldn't).

No abuse on our part. It's essentially the same rear-end as in a Corvette; a well tested and proven component. The touchy seals are common in those too.