I have an 89 RS with a 90 3.23 rear. Can i use a 91 posi from a 2.73 gear car on my 90 rear end with a 3.23 gear?

Bottom line: can i use a 2.73 posi from a 91 iroc on my 3.23 rear? assuming they both have 28 spline axels.

 

The 3.23 gears are 3 series gears, and the posi that has the 2.73s on it is a 2 series carrier. You can use those gears on that posi, if you get a spacer that allows you to run 3 series gears on a 2 series posi. As long as you have the right axles then everything will bolt up correctly, and fit right. Its just a matter of getting the right series gears and posi.

 

i thought that the only difference between 2 and 3 series were the carriers. Like 88 and down and 89 and up were all 3 series carriers.

 

its not really a year thing, more like the ratio that depends on the carrier number.

the year thing could be placed for the axle splines. 89+ had 28 splines. verses 26 from previous years.

 

The difference in the carries is in the gear ratio they use. 2.72 - 3.08 gears are mostly 2 series carrier gears, and 3.23 + are 3 series. So if that carrier has 2.73 gears, I guarentee you its a 2 series carrier. The ring gear on the 2 series setups are thicker than 3 series ring gears... hence why you can't put 3 series gears on a 2 series carrier w/o a spacer.

Companies do make higher ratios for the 2 series carries though. I know Richmond does. They are normally a little more $$ than 3 series gears though. I think about $20.

As said, the axles spline #s can be defined by years, as in 26 spline is up to 89, w/ 89 being the transition year to the 28 splines which was 90 +