HI guys,  I dont  know enough about this stuff to know if I have the same problem as THDAVIS but here goes:   whlie im advancing toward a red light with my foot on break it is fine but when I start to slowly advance and  start my turn (with my foot still on brake)  there is a thud thud thud and it will continue until I reach about 10 mph then evrything is fine. It is also fine if I come to a stop and do not make any turn of the wheel.

Sounds like you need to change the fluid in the diff, and add the posi additive.

Mark, By all means, take Ken's idea first. The hard part is getting the old stuff out, as the rear doesn't have a drain. In a older issue of one of the Corvette rags, it tells how to put a drain in, with a template you can buy from a supplier, but that's another story. My situation started the same way as you describe, but quickly worsened. (Is that a word??) Take a look at the rear tires when parked, if the top is cambered in, good chance the axles have started grinding on the pin for the spyder gears. This makes the clutches slip, and bang..bang.. bang. I certainly hope that changing the lube will do it. Otherwise it gets spendy reallllll fast.

Thanks Ken I'm gonna try that tomorrow Tues. 15th I'll let you know how that went.

  David I sure hope it is not what you described (with my car luck it will be)   one thing I can be sure of is that the back tires point inward  at the bottom not the top.  and that is greatly exaggerated when the car is on lift. I was not ready for that the first time I saw it the car went up and the tires looked like aircraft landing gear pulling in

Anyway we'll see.   Thanks again

Well Ken,  you were right (again)   that is exactly what the deal was:  posi additive added problem solved.    I have driven about 30-40 miles on it since and no noise.    Thanks.

 Thanks David for responding also. I like to get different takes on stuff.

Mark

David was right, but it's always worth trying the basics first.

Glad I could help.