When accelerating, i have a whining noise that sounds like it's coming from my differential. But then it changes to like a rubbing noise for every wheel revolution when decelerating below 40 mph. I've check the differential fluid and it's at the right level. Time for a new rear end? It's on my '99 Trans Am, has 51,000 miles on it. The rear end is a 3.23 ratio, limited slip (posi-traction) differential. Thanks for the advice in advance.