Transfer case engagement and disengagement system

Abstract

An automotive vehicle has a transmission through which an engine can deliver torque to an axle to propel the vehicle and a transfer case associated with the transmission for operating auxiliary equipment. A system for engaging and disengaging the axle from the transmission and for engaging and disengaging the auxiliary equipment contains a first solenoid (,) that operates to a first state when the vehicle is to be propelled and to a second state when the auxiliary equipment is to be operated and a second solenoid (,) that is selectively operable to a first state that causes the auxiliary equipment to be disengaged from the transmission and to a second state that causes the auxiliary equipment to be engaged with the transmission through the transfer case. A module (,) controls the solenoids and receives a first input (,) for requesting concurrent operation of the solenoids to their respective second states, a second input (,) for signaling transmission output shaft speed, and a third input (,) for signaling full engagement of the auxiliary equipment with the transmission through the transfer case. Once the third input has signaled full engagement of the auxiliary equipment with the transmission through the transfer case, the module prevents both disengagement of the auxiliary equipment from, and engagement of the axle with, the transmission until the second input signals a speed predetermined to be a speed suitable for allowing both disengagement of the auxiliary equipment from, and engagement of the axle with, the transmission.