I went through my RPO codes and found some interesing things about my '86 IROC, but mainly it this caught my attention.

G80 - Rear Axle, Limited Slip Differential

Is it a GM piece or from somebody like Eaton? Niether service manuals show anything about it.

 

I thought they were borg-warner. There should be a tag on it somewhere unless its been broken off.

 

GM used about three different designs of Limited Slips (RPO G80)in 3rd gen cars. There is NO way to tell which one you have until you open up the rear diff. Picture is the most common designed used.