PURPOSE: To attain compactness and simplify constitution in the differential case structure of a differential gear in a transfer for an automobile by fitting the divided ends of a first and a second cases mutually in the overlapped state, and passing a differential pinion shaft through the overlapped parts to connect both cases.

CONSTITUTION: A differential case 21 is of combined structure divided into a first and a second cases 38, 39. These cases 38, 39 are relatively rotatable on an axis 15 and assembled with divided ends 38a, 39a in the mutually fitted state, that is, the divided end 39a is fitted in close contact into the divided end 38a. A pair of small diameter holes 53, 53 and a pair of large diameter holes 54, 54 are then formed at the peripheral walls of the divided ends 38a, 39a of both cases 38, 39, in the radially symmetric positions from the axis 15, and both holes 53, 54 are brought in line at the fitting time. The small diameter shafts 50 and large diameter shafts 49 of a differential pinion 25 are respectively fitted into the small diameter holes 53 and large diameter holes 54 to connect both cases 38, 39 and to support the differential pinion shaft 25.