PURPOSE: To reduce cost with reduced number of components and facilitate maintenance checkups with simplified access to each mechanism by supporting and enclosing one axial end side of a rotary shaft of each mechanism with a main case section and supporting and enclosing the other end side with the front or rear case section.

CONSTITUTION: One end side of a differential gear case 60 and a transfer gear shaft 52 as a rotary shaft of a differential gear section 48 and a transfer gear section 46 is supported and enclosed with a main case section 66 via bearings 72, 74, 76 and 78. The other end side is supported and enclosed with either a front case 68 or a rear case 70 via bearings 80, 82, 84 and 86. As a result, counterparts of conventional components such as subcase, front cover, and rear cover case are not required. The number of components constituting a transmission case 8 is reduced even if an oil pan 124 is included. Each mechanism is easily accessed by removing either front or rear case section 68 or 70 and maintenance checkups are facilitated.