my 91 rs has problems with it's rear end. It shakes when I'm going around 50 mph. I changed the wheel bearing and the tire still wiggles and only on the back right side cause I switched the rear tires and it's only on that side. when I opened the diff. case I noticed that the case and pinion shaft had grind marks on them. Also the top thrust washer was stuck to the magnet. Has this happened to any one before? I would like to know if a 96 trans am 10 bolt posi unit will fit in my 91 rs? any help will be great thanx.

 

It should work but the new rear end out of a 4th gen is 4 or 5 in wider. I have a 91 and am about to do the same thing. Right now I have newer model wheels on my car with 2 1/2 in spacers all the way around so that I can get a 10 1/2 in tire snugged in there. With the new rear end I will be able to toss the spacers on the back tires.

 

They can be swapped in with no major problems. Just note they are 4" wider overall.