I researched the RPO codes from my 89 RS and I've found I have 2.73 gears (GU2) which tells me I have a 2 series carrier. I already know I have an open differential, but what I don't know is how many splines my axles are cut to.

I've read that the splines for Camaro axles were changed from 26 to 28 in 1989. Some say it was beginning, some say it was mid year. My car shows it was produced in May (5/89)- so how many splines do my axles have?

And if I were to buy a 3 series posi unit and 3 series gears to replace the current internals will they fit without modification in my stock rearend? (I know they make 2 series posi units and gears I'm just thinking about cost- now and for the future). Thanks in advance.

 

Just a guess, but what you say about the build date and being a 2:73 10-bolt don't count on having 28 spline axle shafts. Only way is take one out and verify what you do have, before buying any parts.

 

I was scrathing my head about the 2.73's... I've taken my car to the track a few times and made some decent passes with other than decent times. I believed all along I had 3.08's in the back. Having 2.73's would make me feel a little better about the times but knowing my luck it wasn't going to be that simple.

So I looked up a few gear ratio calculators and ran some tests. (on the way home) For some reason everything checks out as if I had 3.08's.

Whatever I have back there is certainly a 2 series, so I'm not real concerned. And yeah I can peek at the axles to see how many splines I have- was just hoping someone had definitive knowledge. What about the 2- to 3-series swap?

 

If you have RPO GU2 and your car is a Auto the rear ratio is 2:73.
Only Manual tranny cars had the 3:08 no matter what your calulations are. Not that much difference between the two.

 

I had a 3 series but that shouldn't matter. I got an Auburn Pro Series Posi with Richmond Gears 3.73. Get new bearings throughout and don't skimp on the seals or you will regret it. Get the entire kit.