I have an 89 IROC w/ a 5.7 TPI. It came w/ nearly every option available. It has 4 wheel disc brakes, power everything, etc. I am having trouble identifying the gear ratio that I have. I am also not sure if the rearend has positraction or not. I found a tag on the differential that says something along the lines of "Anti-Slip". It is a BorgWarner rearend. If someone could help me identify the gear ratio and whether or not "Anti Slip" means positraction, I would really appreciate it.

 

count the cover bolts, that'll tell you what rear. pull the cover and count the gear teeth and do the math, or look for the teeth count stamped on the ring gear and do the math, that'll give you the ratio. limited slip is posi, anti slip would be the same. add soem fresh oil and posi additive from gm parts if it's clutch type posi.

 

The only way to know for sure is to pull off the cover and look. If you haven't changed the fluid lately, then it needs it anyway; make a point of looking at the gears while doing the overdue routine maintenance.

Most likely, the car came with a 2.77 gear, which was the standard ratio for that drivetrain combo.