Patent ID: 8771128

Claim:
A drivetrain for a motor vehicle having a power source and first and second sets of wheels, the drivetrain comprising: a first driveline adapted to transfer torque from the power source to the first set of wheels; a power take-off unit including a first hypoid gearset and a first disconnect coupling for selectively interrupting the transfer of torque between the first driveline and the first hypoid gearset; and a second driveline adapted to transfer torque from the first hypoid gearset to the second set of wheels, the second driveline including a propshaft driven by the first hypoid gearset, a second hypoid gearset driven by the propshaft, a differential assembly driven by the second hypoid gearset, and a second disconnect coupling for selectively interrupting the transfer of torque between the second set of wheels and the second hypoid gearset, wherein the differential assembly has an input driven by the second hypoid gearset, a first output driving a first axle shaft adapted to drive one of the second set of wheels and a second output driving a second axle shaft adapted to drive the other one of the second set of wheels, wherein the second disconnect coupling is configured to selectively connect and disconnect the second output of the differential assembly to the second axle shaft, the second disconnect coupling including a multi-plate clutch operably disposed between the second output and the second axle shaft, and a ball ramp clutch actuator operable for axially moving an apply plate relative to the multi-plate clutch, wherein the ball ramp clutch actuator includes a first cam member having a first groove, a second cam member having a second groove, and a roller disposed in rolling engagement with the first and second grooves, wherein relative rotation between the first and second cam members causes the second cam member to translate for axially translating the apply plate, wherein the first groove defines a first angled portion and a second angled portion, wherein the second groove defines a third angled portion and a fourth angled portion, and wherein the first and third angled portions have the same angle and extend along complementary lengths of the first and second grooves, respectively, to establish a first rate of axial apply plate travel in response to the relative rotation between the first and second cam members and, wherein the second and fourth angled portions have the same angle, different from the first and third angled portions, and extend along complementary lengths of the first and second grooves, respectively, to establish the second rate of axial apply plate travel in response to the relative rotation between the first and second cam members, wherein the first rate of axial apply plate travel is larger than the second rate of axial apply plate travel, and wherein the ball ramp clutch actuator reduces frictional losses by maximizing distances between elements of the multi-plate clutch when disconnected.