Abstract: A transfer case including a hydraulically actuated torque-coupling device is provided for selectively actuating a secondary drive axle of an All-Wheel Drive motor vehicle when wheel slippage occurs with a primary axle. The transfer case comprises a housing, an input shaft and an output shaft both rotatably supported within the housing, and the torque-coupling device. The torque-coupling device comprises a hollow casing, a selectively engageable friction clutch assembly for operatively coupling the input shaft to the output shaft, and a hydraulic clutch actuator. The hydraulic actuator includes a hydraulic pump located within the casing and adapted to generate a hydraulic pressure to frictionally load the friction clutch assembly, and a variable pressure relief valve assembly fluidly communicating with the hydraulic pump to selectively control the hydraulic pressure generated by the pump.