Any help would be greatly appreciated. Sorry for the long post.

On occasion when I shift into reverse and drive the car slowly I hear and feel a noise coming from the rear end area that feels like a ratcheting noise or metal catching and releasing. Also seems to happen more when turning in reverse than when going straight and level. I cannot make it do this all the time, maybe 1 out of 20 times. If I hang out the car when it is happening and watch the rear drivers wheel I can physically see the rear wheel slightly bind and release the load. Seems to happen more if I hit the brakes and bind things up before moving in reverse, then if I shift to drive it will do it for the first 2-3 revolutions of the wheel then free up completely.

96 Z 28, 2.73 rear end, 90,000 miles. Replaced front and rear pads and rotors & trans mount (needed it anyway) and greased calipers. Pistons compressed fine and sliders move fine. No change.

Also have replaced the rear end lube with 75-90 Mobil 1 ls, no additive. Have some additive coming this weekend from dealer to see if it fixes the problem as it seemed to start around the time I changed the diff fluid. But it is hard to know as I have only owned the car for about 1000 miles. When I had the cover off everything looked good, but I do not have a ton of experience with RWD diffs.