Differentials
The accompanying Interchange Chart, and Gear Ratio Chart, show the stock ratios available and possible swaps. The keys to interchange are driveshaft flange, axle spline (with outer wheel bearing diameter), and inner CV joint bolt pattern (for 86-92). For 79-85 entire axle assembly swaps, be sure not to mix drums, shoes, brake backing plates when mixing the 79-80 style with the 81-85 style, or backing plates when mixing 81-83 with 84-85.
| YEARS | PART | NOTES |
| 79-85 (12A) | Complete axle assembly | Brake line threads changed in ’81, shoes drums, and adjusters are much better 81-85. Driveshaft flange changed in ’83. |
| 79-83 (12A) non LSD | Bare axle housing | Interchangeable |
| 84-84 (12A) non LSD | Bare axle housing | Interchangeable |
| 79-83 | Bare axle | Interchangeable |
| 81-83 | All | Interchangeable except must match w/LSD and driveshaft / flange (larger in ’83) |
| 79-83 | 3rd Member | Interchangeable except must match driveshaft and flange (larger in ’83) |
| 84-85 | 3rd Member | Interchangeable |
| 86-92 All non-turbo | 3rd Member assembly | Interchangeable |
| 86-92 Turbo into non-turbo | 3rd Member assembly | Must use custom driveshaft #2691-799R, and use Turbo halfshafts |
| 89-92 4.3 viscous LSD into non-turbo | 3rd Member assembly | Bolt-in, must use LSD stub axles |