Abstract: A part time four wheel drive vehicle has an axle disconnect in its auxiliary drive axle. The axle disconnect has a clutch sleeve non-rotatably and translatably mounted on an inner axle shaft so that the clutch sleeve translates between a first position where clutch teeth of the clutch sleeve engage clutch teeth of an outer axle shaft and a second position where the clutch teeth disengage. The clutch sleeve includes an integral annular piston that is part of a coaxial motor that shifts the clutch sleeve from one position to the other in conjunction with a return spring. The vacuum motor communicates with an external vacuum source and the axle disconnect includes a float valve for sealing a vacuum port of the vacuum motor to protect the external vacuum source against contamination if the vacuum motor is filled with lubricant in the axle housing leaking into the vacuum motor housing.

Abstract: A control system for a full time four wheel drive vehicle having a transfer case including a planetary gear differential and an electromagnetically actuated clutch assembly for biasing torque between the front and rear drive wheels in response to signals from the control system. The control system includes apparatus for detecting wheel slip and a device, responsive to the detection of wheel slip for calculating a maximum torque level to be established by the clutch assembly as a function of the total torque delivered to the transfer case and for programming clutch torque application over a predetermined time period and in a manner biasing torque through the differential to eliminate wheel slip.