PURPOSE: To easily position a transfer mechanism by installing a transfer mechanism onto a differential gear case and engaging a restricting member and a side gear by the transfer mechanism and revolving the side gear integrally with the differential gear case.

CONSTITUTION: A transfer mechanism 19 for shifting a restricting member 14 in the axis line direction of a left side wheel driving shaft 13 is installed onto the outer peripheral side of a differential gear case 6 on which the restricting member 14 is positioned. Side gears 10 and 11 and the differential gear case 6 are revolved integrally by the engagement of the restricting member 14 and the side gears 10 and 11 by the transfer mechanism 19. Therefore, the engagement with the restricting member is permitted, and the transfer mechanism can be easily positioned.