How do I know if I have the 7.5" or the 7.625" rear? or even the 9 bolt? It´s a 89 Camaro RS 2.8L M5 (original now it has 327 and T56)

 

assuming its origional, its a 10 bolt, 7.625.
count the cover bolts, 9 is a 9 bolt 10 is a ten bolt.

 

ok thanks,

what cars came with the 8.5"?

 

No factory third gens came with a 8.5".

The only thing that comes close is the SLP Firehawk. It came with a Dana 44 which is an 8.5".

The Dana 44 was an over the counter replacement diff once offered by GM. They're pretty rare now. Chances are if you find one that's not trashed, it can be cheaper to just buy an aftermarket 12 bolt or 9".

 

ok, i guess im just going to straighten that baby 7.625" with girdle and real 28 spline axles. But on the other hand if my original v6 car came with 7.625" like //<86TA>\\ said, what 3gens came with the 7.5"?


p.s. excuse my English, I´m from Iceland

 

7.5" and 7.625" are the same thing for all practical purposes. The only difference is that in some year around 86 or 87, the factory made the outer diameter of the ring gear slightly larger. Nothing else changed. AFAIK all replacement gears nowadays are the larger size. All parts interchange; gears, bearings from 80 up, carriers, axles subject to their spline count agreeing with the side gears in the carrier, etc.

Most of these cars came with the 7.5"/7.625" 10-bolt. The only ones that got the 9-bolt were some (not all) of certain Firebird models (TA, GTA, Formula) from 85 to 89, and some (not all) IROC Camaros from 87 to 89. A very very few early production 90 models got them, but those were only leftovers from the 89 model year.

 

there is a difference, the ring and pinion interchange no problems, the innards, spidergears and such, are a little different. There is 1/8" more room side to side inside the carrier of a 7.625 rear than a 7.5. though this is usually not a problem cause people would just swap the whole carrier when they want a posi or something. I just know this because i made the mistake of buying a powertrax a while ago and found this little tid-bit of info out.