The DEHA(Direct Electro-Hydraulic Actuator) 4WD system is an automatic variable 4 wheel driving gear. This system distributes an optimum driving torque to front and rear wheels according to a driving condition(a road condition or driving condition). The 4WD ECU receives sensor inputs through CAN communication and determines the power distribution for the front/rear wheel. Then it controls a coupling system to transfer driving torque to rear wheels.