To lightly and easily perform a hand-push operation of a traveling machine body when a propeller shaft for traveling is freely rotated.SOLUTION: An input gear 40 is provided with a locking part 40b for transmission. A shift gear member 43 provided with a to-be-locked part 43a that is engaged with or disengaged from the locking part 40b for transmission is provided. A boss member 32 having a slide engagement part formed on an outer peripheral side thereof is externally fitted and attached to a propeller shaft 3R for traveling, so as to be relatively rotatable. On the propeller shaft 3R for traveling at a position further apart from the input gear 40 than the boss member 32, a slide engagement shaft part 33 is formed which is able to engage with an inner-peripheral slide engagement part 43b of the shift gear member 43. The shift gear member 43 is configured so as to be able to change its location among a differential lock position a1, a differential actuation position a2, and a free rotation position a3 at which the locked part 43a of the shift gear member 43 is disengaged from the locking part 40b for transmission and the inner peripheral slide engagement part 43b is engaged with the slide engagement shaft part 33 at a position apart from a slide engagement part 32a.SELECTED DRAWING: Figure 4
