Transfer Case Functions

There are three transfer case modes, Auto, 4WD Low, and 4WD High. Neutral is only available as a dealer installed option.

CONTROL-TRAC FUNCTION
The Control-Trac transfer case uses an electromechanical clutch assembly to control torque to the front wheels. In the Auto mode, while at rest and under cruising conditions, the GEM activates the transfer case clutch at a minimum level. This allows for the slight difference between the front and rear driveshafts which occurs normally when negotiating a comer on dry pavement. Under any of the following conditions, the GEM will increase the torque sent through the clutch to the front wheels in order to prevent or control slip.
- Slip is detected (by monitoring the front and rear OSS sensors in the transfer case)
- Throttle position (by using the throttle position signal from the EEC)

RANGE FUNCTION

NOTE: At zero throttle, the duty cycle remains low. At very light to heavy acceleration, the duty cycle jumps to the maximum.

In the 4WD Low Range, with throttle input, the transfer case electromechanical clutch locks the front and rear driveshafts for maximum 4WD traction. The transfer case shift motor rotates the shift cam to move the reduction shift fork to the 4WD low range position. This low range shift, accomplished through a planetary gear set, changes the torque to the driveshaft from 1:1 to 2.48:1 ratio.
In the 4WD High Range, with throttle input, the GEM signals the transfer case electromechanical clutch to lock the front and the rear driveshafts for maximum 4WD traction. Never use the 4WD High range when driving on dry or merely wet pavement. Use the 4WD High range only for driving off-road or in severe winter weather.