I am not quite sure if the GTA I have came with the 3.23 or 2.77 rear gears. I am inclined to say the 3.23 as at 80 mph it is up to about 2700 rpms, though I am not sure. I am also unsure of what differential was placed from the factory on F-body's in the late 80's. In changing the diff gasket last week, I noticed it was a 9 bolt and on the inside it had the letters BW (which I am assuming stands for Borg-Warner whom I thought only made trannys and the occassional movie too . I believe I saw the #'s 3.23 on there as well. Was this the stock unit? Any info will help.

Peace,

 

gm used 9 and 10 bolt rears, does it really matter what it left the factory with as much as what's in it now? count teeth and do the math and you'll know what you have.

 

Sounds like you've got 3.23's. I've got a 2.77 9-bolt and 80 mph comes at an even 2000 rpm.

It probably was the stock unit, and the stock gearing. If you 've got disk brakes, you've got a pretty good axle there.

 

If I remember correctly, the 10-bolt has 3.23's, the 9-bolt 3.27's.

JamesC