Select Drive System

The Select Drive is a system which permits the full time four wheel drive power train to be operated in a two wheel drive mode. When the vehicle is stopped, the system can be changed from two wheel drive to four wheel or four wheel drive to two wheel drive, by pulling the instrument panel control switch pull release pin downward and moving the control switch lever to the desired position. The two major components of this system are a shifting device in the transfer case and a disconnecting mechanism in the front axle, which are controlled by the instrument panel switch through a series of vacuum actuators.
The vacuum actuated shifter mechanism located on the transfer case slides a splined clutch, located on the transfer case main shaft, rearward to engage or forward to disengage power to the front drive chain sprocket. In the two wheel drive position, the shifter mechanism also locks the transfer case differential. Also the main shaft and differential assembly will turn as a unit, transferring power to the rear driveshaft, while front output shaft, chain and sprocket remain stationary.
A vacuum actuated disconnect device is used to engage or disengage a splined clutch that connects the righthand driveshaft to the righthand half shaft. When four wheel drive is selected, the spline clutch is engaged and the front drive axle operates in a normal manner. When two wheel is selected, the vacuum actuator releases the spline clutch, which releases drive to the righthand half shaft and allows the righthand driveshaft to rotate freely. Due to the design of the differential, to equalize torque between left and right axle shafts, disconnecting the right axle shaft will allow the left axle shaft to rotate freely. The axle disconnect will not release all front drive components in the two wheel drive mode. Half shafts and different side gears will continue to rotate with the front wheels as the vehicle is driven.