On this forum, everyone has stated that the "guts" of a differential, the posi, carrier, ring and pinion will interchange among all 8.5 rear axles. However, I have found that there are two methods for attaching the axle, c-clips and bolts, and two spline counts on the axles, 28 and 30. Will the guts still interchange no matter what spline count and attachment method you have?
71-88 used 28 spline axles on the corporate carries. 89 went to 30 spline axles. Chevy uses C-clips. BOP rears are bolt-in axles. So....you need 28 spline axles in your 71-2 Skylark rear to go into the 28 spline posi carrier.
One can always swap c-clip 8.5 posi carriers into bolt-in axle 8.5 rears. When one has a c-clip rear & an early 8.5 posi carrier that was original to a bolt-in axle rear, one can have problems. The early bolt-in axle 8.5 carriers don't have the c-clip recess's, so if trying to use in a F-body or Nova rear, one will have to either machine recesses in the side gears, or use a different carrier. :3gears: Roger
