can anybody help with this problem.I have a 1985 iroc z28 305 the rearend i have is the original. numbers are 8ka gear ratio 3.42 trying to swap differential to a powertrax posi.heres my question what sizes differential I have now could be 7.5 or 7.625?also axle splines are they 26 or 28?can not find info unless tear down rearend.really don't want to do this and then wait for parts some body has to know checked all books and all other resources

 

Your 85 will be probably 7.5". The 7.5" and 7.625" is really the same when ordering parts. GM upgraded the gear size around 1986 but it's just a slightly larger gear on the same carrier. Everything else is the same. You have 26 spline axles.

 

ok so in light of htis question, where can i get a new carrier(posi unit) and gears for my 92 rs? i do not want to have to throw in an entire housing, jsut the carrier and gears.

also what gear size would still keep it reasonable for higway cruising

92 rs
700r4 tranny