Abstract: A differential (100) includes a clutch pack that is activated by rotational movement of a ball ramp (31) that results in a linear force applied to the reaction plates (41) and friction plates (42). The ball ramp (31) is controlled by a DC motor (114) that has a high efficiency of a gear train to allow the use of the DC motor to control the activation of the clutch pack.

Abstract: An all-terrain or utility vehicle having various combinations of left and right front wheels, left and right rear wheels, a differential rotationally variably coupling the left and right front wheels together with a variable coupling torque and a source of motive power being selectively coupled to the left and right rear wheels in one configuration and coupled to the left and right front wheels as well as to the left and right rear wheels in a second configuration. The coupling torque is relatively stronger when a speed of the vehicle is relatively slower and is relatively weaker when the speed of the vehicle is relatively faster.