A system for applying independently variable torque to the drive wheels of a vehicle comprising: a clutch housing, a clutch pack mounted in the housing wherein the clutch pack includes interleaved annular friction and clutch plates (52, 54, respectively), said friction plates fixed for simultaneous rotation about a centroidal axis of rotation independently of fixed simultaneous rotation of said clutch plates, wherein one of either said friction plates or said clutch plates are fixed for rotation with at least a part of said clutch housing which rotates with a corresponding drive wheel, and the other of said friction plates or said clutch plates is fixed for rotation with a drive shaft of the vehicle, a resilient member within said clutch housing biasing by a resilient force applied by said resilient member, said clutch pack into a fully locked mode, wherein in said fully locked mode said friction plates and said clutch plates are compressed together so as to frictionally inhibit relative rotation between said friction plates and said clutch plates about said axis of rotation, a selectively actuable actuator within said clutch housing, selectively actuable so as to engage said resilient member and thereby to selectively relieve and reduce said resilient force applied by said resilient member to said clutch pack, characterized in that said resilient force is said selectively relieved and reduced to either unlock said clutch pack completely, or progressively relieve said clutch pack by an amount sufficient to allow limited relative rotation about said axis of rotation between said friction plates and said clutch plates to thereby provide a selectively optimized amount of rotational traction versus rotational slippage to maximize steering and handling performance of the vehicle in cornering while minimizing loss of drive traction between the drive shaft and the associated drive wheel, and in that the vehicle has a laterally opposed pair of left and right drive wheels, said system further comprising, corresponding to the left and right drive wheels, left and right clutches each comprise of said clutch housing, said clutch pack, said resilient member and said actuator, further comprising an actuating sub-system to said selectively actuate said actuator in each said clutch wherein, during said cornering, said actuating sub- system said actuates said actuator in said left clutch to a different extent compared to said actuation of said actuator in said right clutch to thereby provide different rates of said relative rotation between corresponding said friction and clutch plates (52, 54, respectively) between said left and right clutches, and in that each said actuator is a hydraulic actuator, and wherein said actuating sub-system includes a hydraulic steering pump of a hydraulic steering circuit of the vehicle. a clutch housing, a clutch pack mounted in the housing wherein the clutch pack includes interleaved annular friction and clutch plates (52, 54, respectively), said friction plates fixed for simultaneous rotation about a centroidal axis of rotation independently of fixed simultaneous rotation of said clutch plates, wherein one of either said friction plates or said clutch plates are fixed for rotation with at least a part of said clutch housing which rotates with a corresponding drive wheel, and the other of said friction plates or said clutch plates is fixed for rotation with a drive shaft of the vehicle, a resilient member within said clutch housing biasing by a resilient force applied by said resilient member, said clutch pack into a fully locked mode, wherein in said fully locked mode said friction plates and said clutch plates are compressed together so as to frictionally inhibit relative rotation between said friction plates and said clutch plates about said axis of rotation, a selectively actuable actuator within said clutch housing, selectively actuable so as to engage said resilient member and thereby to selectively relieve and reduce said resilient force applied by said resilient member to said clutch pack, characterized in that said resilient force is said selectively relieved and reduced to either unlock said clutch pack completely, or progressively relieve said clutch pack by an amount sufficient to allow limited relative rotation about said axis of rotation between said friction plates and said clutch plates to thereby provide a selectively optimized amount of rotational traction versus rotational slippage to maximize steering and handling performance of the vehicle in cornering while minimizing loss of drive traction between the drive shaft and the associated drive wheel, and in that the vehicle has a laterally opposed pair of left and right drive wheels, said system further comprising, corresponding to the left and right drive wheels, left and right clutches each comprise of said clutch housing, said clutch pack, said resilient member and said actuator, further comprising an actuating sub-system to said selectively actuate said actuator in each said clutch wherein, during said cornering, said actuating sub- system said actuates said actuator in said left clutch to a different extent compared to said actuation of said actuator in said right clutch to thereby provide different rates of said relative rotation between corresponding said friction and clutch plates (52, 54, respectively) between said left and right clutches, and in that each said actuator is a hydraulic actuator, and wherein said actuating sub-system includes a hydraulic steering pump of a hydraulic steering circuit of the vehicle.