PURPOSE: To make such optimum traveling as making full use of a characteristic of each system attainable, by setting to down to a part-time system capable of selecting 2-to-4 wheel drive and vice versa, while making two types of driving systems of FF and FR at the two wheel drive selectable.

CONSTITUTION: When a claw clutch 34 for a center differential lock is engaged, center differential gears are unitized in one whereby side gears 22 and 23 at both sides comes into a state of being directly connected so as to rotate at equi- speed with an output shaft 5 all the time. Under this condition, when a claw clutch 24 alone is engaged, the output shaft 5 is connected to a front drive shaft 14, coming to two wheel drive of FF. On the other hand, in a state of the claw clutch 34 being engaged, when a clutch 30 alone is engaged, the output shaft 5 is connected to a rear drive shaft 31 via a transfer gear 28, a transfer shaft 29 and the clutch 30, thus coming to two wheel drive of FR.