Does anybody have a link where i can tell what rearend i have by the VIN. I'm gonna go under the car tomorrow and see if i can find the "G code" off the rearend, but i'm looking for a site or link that can list them all by VIN or "G code." Thanks again guys for the help.

 

G80 is for limited slip differential, GU4 is 3.08, GU5 is 3.23, GU6 is 3.42, GT4 is 3.73.

 

I also read somewhere that if the rearend has posi theres a rearward facing tab on the side of the pumpkin. This true? Thanks for your answer big gear head.

 

Yes there should be a tab coming off one of the pumpkin cover bolts if it is posi. This is only if someone hasnt been in there though as by this time most of those tabs are gone.

 

The Vin dose not have any information about the RPO numbers that tell what options are on the car.

 

At this point there's no telling what's been done by previous owners, the easiest way is to compare rpm to mph, if your speedo is accurate.
With 245/50R16 tires, and the 5-speed in 4th or the 700R-4 in third, with the converter locked, here's your rpm at 55 mph.
2.73:1=1966
2.77:1=1992
3.08:1=2213
3.23:1=2323
3.27:1=2353
3.42:1=2457
3.45:1=2484
3.73:1=2680

 

Ok way according to the codes listed above i have a 3.08 gears with posi. They put posi with 3.08's?

 

The G80 limited slip was a extra cost option and could be special ordered on any rear.

 

My '89 Iroc has 2.73 gears(GU2) and posi rear(G80).