This is my first time posting but you guys seem very knowledgeable. I have an 89 RS with a nasty right rear bearing growl and im going to replace it soon but i think the axle is done for also. I looked for the axle code on the rear-end and couldn't find it, i knowits a 10 bolt open diffand the ratio is 2.73from the rpo code but i need to find out the spline count and length to order a replacement. Any help would be awesome

 

1989 was the change over year from 26 to 28 splines. Now you quote a 2:73 open rear, my guess is you have 26 splines because GM had a large inventory of those common axle assembies. To be sure, you have to check the spline count yourself. There is no axle code or RPO number that will indicate the spline count. Length is common to all 10-bolt regardless of year for all 3rd gen cars. 4th gen & 9-bolts length are different.

 

Alright that helps me out thanks for the help now i just hope the axle doesn't need to be replaced when i pull it.Thanks again