Two sizes of differential assemblies are used on American Motors cars; 7 9 / 16 in. (192mm) and 8 7 / 8 in. (225mm) ring gear units. A twin-grip limited slip differential is available as an option on both units.
See Figure 1
A letter code used to identify the axle ratio will be found on most differentials, stamped on the right axle tube housing boss, on the rear side, adjacent to the dowel hole. Some earlier cars have either a metal tag attached to one of the bolts of the differential housing cover or the code letter stamped on the right differential housing cover flange. It may be necessary to remove the cover from the differential to locate the letter. The codes and the axle ratio are listed in dealer parts guides and shop manuals.
The 79/16in. (192mm) axle can be identified by the cover mounted filler plug, and the 87/8in. (225mm) axle by the front filler on the housing.