Coupling device comprising a hydraulic pump

A device for coupling an input shaft (24) and an output shaft (26) is provided. The device preferably includes a carrier coupled to the input shaft, a hydraulic pump (14) coupled to the carrier and the output shaft, a hydraulic conduit (16) coupled to the hydraulic pump, a piston (18) coupled to the hydraulic conduit, a clutch (20) coupled to the piston, and a control valve (22) coupled to the hydraulic conduit. A twin coupling device of this type may be used in a four wheel drive vehicle.