I read the FAQ and I dont really have the means to jack both my rear wheels off the ground and spin them around and I dont want to waste the gear oil by taking off the cover of the rear end. Can some one please tell me if my car a 1991 RS with a 305 Auto. Came with any kind of limmited slip or does it only produce a " one tire fire" as it is called. Is it possible to order this option with that car? .

 

Do you have an RPO list? If you have G80, then you have a posi. There's no other way to "guess" if your car has a posi or not. There's no reason a previous owner couldn't have changed the diff completely or just the internals. The only way to know for sure what's in the diff is to pull the cover and have a look. Chances are the oil is still original and should be replaced anyway.

A 91 RS with a 305 and automatic came with 2.73 gears. Not a great gear ratio even if you do have or plan on getting a posi. Your car however has 28 spline axles so at least the diff is stronger than the 82-89 versions.

 

Hey, Thanks! I could probably get that list some how. Where would it be? Is it that sticker that's on the inside of the door? I dont have any plans for changing out anything now. The car is all stock and Its my DD and my only car so I'm just gonna leave it how it is. It drives great. I like the low gears on the highway. They seem to keep the RPM's real low.

 

Yeah, the sticker located inside the console glove box should have your options printed on it, i.e. "service parts identification label". If G80 is listed, then you have a posi, and I'll bet you'll have GU2 on there. GU2 denotes a 2.73 gear ratio.

 

Unless you know for 100% certainty when it was last changed, the rear is likely long over-due a fluid change anyhow.

 

Not to beat a dead horse, but the RPO codes will only tell you what the car was originally equipped with, not necessarily what's in the car now.

JamesC

 

Everything stated above definitely rings true as well. If the rear has ever been swapped out, the option label is useless. I also have to agree with Stephen that 2.73's are the most pathetic ratio ever put in these cars. I ditched the 2.73's in my 89 RS 305 years ago for a posi/pbr disc rear with 3.23's, and it was a vast improvement in takeoff power and didn't really affect freeway manners at all. 3.23 and 3.42 are probably the most ideal ratios for all around performance/driveability.