Hi all, as part of my TII conversion of my '80 SA, I was wondering how well the stock 12A diff will hold up to the power of the 1991 TII engine. I am keeping the TII tranny as well, so the drivetrain is good through there, but from there back? Looking at the manuals, I see a major difference in length between the 1991 (S4 or S5?) diff, so I know I'll have to have a custom driveshaft made or have the SA shaft cut down, but will I be grenading the diff the first time the turbo spools up? If it orginal diff won't hold, is there a LSD that I can bolt into the original 1980 diff case? Any help would be appreciated.

 

First off you will need a driveshaft made. The SA diff will not hold the power. The SA diff is also non-lsd. If you are wanting the strongest factory setup and keep the same 3.91 gear, look for a 84-85 GSL rear end. Strait up swap, and you pick up four bonuses. One, you will enjoy the LSD. Two, you will have a stronger rear end with larger axles (If you want to upgrade them, you can get Moser axles from Billy at Re-Speed). Three, you will gain rear disk brakes. Four, you keep your 4X110 wheel bolt pattern.