Patent ID: 6883657

Claim:
A power transfer assembly for use in a motor vehicle having a powertrain and first and second drivelines, comprising: a first shaft adapted to transfer drive torque from the powertrain to the first driveline; a second shaft adapted for connection to the second driveline; a transfer clutch operably disposed between said first and second shafts; an apply plate operable in a first position to exert a minimum clutch engagement force on said transfer clutch and in a second position to exert a maximum clutch engagement force on said transfer clutch; and a clutch actuator for controlling movement of said apply plate, said clutch actuator including a first piston disposed in a first chamber, a second piston disposed in a second chamber, a closed hydraulic fluid circuit interconnecting said first and second chambers, a nut fixed to said second piston, a lead screw in threaded engagement with said nut, and an electric motor for controlling rotation of said lead screw via a reduction gearset operably disposed between a rotor shaft of said electric motor and said lead screw, said second piston being a closed-ended cylindrical member extending forward of said nut and concentrically mounted over an end of said lead screw and being provided with a seal between said second piston and said second chamber.