I recently went to one of the race car guys I know and ask him to fix my ring and pinion.I had a 3.90 put in with a spacer last year which didnt last long.That was behind a 355.Im now going to install a 406 in my IROC and was told that Im wasting my time with my 71/2 rear and that I should get a 8 1/2.My question is do I need a completely different rear or can I get a 8 1/2 posi unit in my rear which is originally a 71/2.If I need a completely different rear which car can I get it from that will match up to an 89 IROC.Thanx

 

Only a aftermaket rear axle asembly made for 3rd gen will work, Nothing found on another non-3rd gen cars is compatable without extensive and expensive Fab work. NO, only internals made for the 10-bolt 7.5/.625 can be used.