Patent ID: 8177673

Claim:
A compact transmission including a clutch unit for controlling power transmitted from a bevel gear unit coupled to an output shaft of an engine, the clutch unit having a forward clutch part and a backward clutch part which are respectively coupled to a forward drive gear and a backward drive gear through a forward coupling and a backward coupling and then to a differential gear part, so that power is transmitted from the differential gear part through a main drive shaft and an axle assembly to a reduction gear assembly, wherein the clutch unit comprising: a subsidiary forward clutch part including one or more friction plates coupled to an inner peripheral surface of an axle housing of the clutch unit; a subsidiary coupling coupled to the backward coupling through a one-way bearing; one or more friction disks coupled to an outer peripheral surface of the subsidiary coupling, the friction plates and the friction disks being arranged alternately; and a piston disposed on one side of the friction plates and the friction disks, wherein, when a vehicle moves backwardly on an upward slope while the vehicle is driven forwardly, an application of hydraulic pressure to the forward clutch part is interrupted and hydraulic pressure is applied to the subsidiary forward clutch part, so that the piston is moved by the hydraulic pressure to compress the friction plates and the friction disks, thereby fixing the subsidiary coupling to the axle housing.