I have a 70 351W 2V Mach with a 9" 3.00 differential. When I am driving or coasting in gear there is a slight grinding noise in the back of the car. If you put the trans in nuetral on the roll the noise stops. At first I thought it was the trans or brakes. I pulled the rear drums and adjusted them. I even apply them while rolling in nuetral and no sound from them. I was told there are 2 bearings in the diff. that deal with load and that these may be bad. Any thoughts? I am not so good on this matter.