I've got a '89 Formula Firebird with:
-LO3, 700R4, and 2:73 open diff rear end.

Im planing on getting 3:42 or 3:73 rear gears and the SLP-take-off posi and was wondering if anyone knew what axels I had.

Im not even sure if it matters what axels I have when purchasing the gears and Posi, but I just wanted to make sure.

Thanx, Ben

-'89 Formula Firebird
All stock except Dunlop 5000 tires
16.263 @82.8mph (Dragway 42)

 

you have 28 spline axles. they are the correct axles for use with the slp take out posi units.

later
tim

 

Do I? I have the exact same car, if his is red. I have the original papers that it came with new. It looks like it was bought in the summer of '88, but it's an '89 model. Is it definite that this car would have the 28 spline axles?

 

I'd guarentee that both of you have 26 instead of 28 spline axles. I've been down this road as well as many others and few had 28 splines in 89.

Take the axles out of that 91 that you have. Those ARE 28. 90 and above is the year that you can bet the farm that they have 28.

Its easy to check. Do a search for the instructions.

 

RGZ is correct. Every 89 10-bolt I have seen posted on thirdgen.org had 26 spline axles. The change over didnt happen for sure until 1990 models.

And why isnt this post in the tranny/drivetrain forum?

 

people have complained in the past about their posts getting no attention in the tranny/drivetrain forum.

 

I second that.....when I went to put in my posi/3.73, the guys at Auburn told me I had 28 splines...but when I pulled it all apart, turned out that I had 26 spline. My car is an '89.