Transfer Case: Description and Operation
OPERATIONWhen the Ignition Switch is in RUN and the four-wheel drive control lever is engaged, the transfer case switch closes and battery voltage is supplied across the front axle actuator. The front axle actuator energizes and the four-wheel drive gears are meshed. This meshing action of the four-wheel drive gears closes the front axle switch, and battery voltage is supplied through the PPL (420) wire across the four-wheel drive indicator lighting the bulb.
Battery voltage is also supplied through the front axle switch contacts and PPL (420) or BRN/WHT (650) wires to the rear-wheel or four-wheel antilock brake module. This will modify the antilock braking system operation in 4WD mode.
A transfer case relay is used on one-ton vehicles equipped with four-wheel drive. This relay is energized when the vehicle is in 4WD mode. From the transfer case relay, voltage is supplied to the transfer case synchronizer.