how can you tell wether you have a 7.5 of 7.625 inch ring gear? i would like to know so i can explore gear set options? also how do you know how many splines it has besides counting them?

 

They're the same thing. It's actually about 7.6", might be metric for all I know. Don't know how the deal about a change in size got started. Gears all fit 78-2002 so they have to be the same.

If you know for certain what year the carrier is, you might infer the axle size... 88-back are certainly 26 spline, 91-up are almost certainly 28; 89 could be either, & there were a few 26s left in 90 it seems. There's no way to be really really certain without counting, since people swap rear ends kind of alot. But that doesn't matter when buying gears.

 

An 86 Iroc could also have a 7.75 9 bolt. If the rear cover has 9 bolts and rubber fill plug, then it's a 9 bolt.

The bigger gear size (ie 7 5/8) and the 28 spline axles were an effort to increase the strength of the 10 bolt so as not to have to import 9 bolts anymore. Unfortunately for GM, the 9 bolt is still much stronger.

It still amazes me that GM continues to put the 10 bolt behind the LS1 Camaros and Firebirds. They put 12 bolts in lesser cars in the 70's.

Miles
Diff Solutions
www.9bolt.com