<p>A differential mechanism comprises a differential case assembly having a casing body connected to a source of drive force and a toothed cap member coupled with the casing body to cover one opened end of the casing body, a plurality of input blocks housed in the case assembly and being movable circumferentially of the case assembly in correspondence with rotation of the casing body, and a pair of output cam members for clamping the input blocks relatively slidably and being independently rotatable owing to a frictional force produced with respect to each of the input blocks to thereby initiate a differential motion on an output side of the differential mechanism. The input blocks are provided in at least two different types and having projected portions. The projected portions of the input blocks of one type have a first upper end width while the projected portions of the input blocks of another type have a second upper end width different from the first upper end width. The casing body has first and second axial grooves provided on an inner peripheral surface thereof such that they extend axially of the differential mechanism. The axial grooves are shaped complementary to the projected portions of the input blocks for meshing engagement therewith. This arrangement prevents misassembling of the differential mechanism. -11-</p>
