PURPOSE:To prevent a clutch gear from being engaged with a brake pawl by requiring greater force for operating a side clutch lever than that for operating the lever after the side clutch is disengaged, and then applying a brake. CONSTITUTION:When a side clutch lever is operated to move a shifter 32 in the direction of an arrow B, a gear 13 which has been engaged with the internal gear 9 of a center gear 8 is separated from said gear 9 against the load of the spring force of a spring 31 so that a side clutch becomes disengaged. The lever can be operated by using a relatively light force because only the spring 31 is contracted. After the completion of said separation of the gear 13, a bowl-like element 29 abuts a separation of the gear 13, a bowl-like element 29 abuts a ring 35 to contract the spring 33. The force required for the operation of the lever is therefore made suddently great, informing a driver of the complete disengagement of the side clutch. If the lever is held in such state, a machine will go forward by the use of the turning force of a left axle 2 only and proceed to swing in the right direction gradually. When the lever is operated from the above state, brake pawls 21 and 30 engage with each other so that the machine is braked and, at the same time, is suddently turned to the right.
