Patent ID: 8312975

Claim:
A hydraulic control system for an all wheel drive vehicle having primary and secondary drivelines as well as an engine transferring power to the primary driveline, the control system comprising: a clutch adapted to selectively transfer torque from one of the engine and the primary driveline to the secondary driveline; a piston slidably positioned within a cavity to apply an actuation force to the clutch; and a hydraulic control unit adapted to receive pressurized fluid from an anti-lock braking system, the hydraulic control unit including a first valve selectively isolating the pressurized fluid of the anti-lock braking system from the cavity a second valve moveable between a first position where the cavity is in fluid communication with the first valve and a second position where the cavity is adapted to be in fluid communication with a fluid reservoir of the anti-lock braking system, a first check valve adapted to restrict fluid flow from the first valve toward the anti-lock brake system, a second check valve adapted to restrict fluid flow from the anti-lock brake system toward the second valve, and a pressure relief valve adapted to permit fluid flow from the cavity toward the fluid reservoir when the fluid pressure exceeds a predetermined value.