C-Trac Function
The C-Trac transfer case transmits torque to the front wheels through an electromechanical clutch assembly. In the Auto mode, while at rest and under cruising conditions, the Generic Electronic Module (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 corner 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.
l Slip is detected (by monitoring the Hall Effect Sensors in the transfer case)
l Heavy acceleration (by using the throttle position signal from the EEC)
l Very light or zero throttle at speeds above 64 km/h (40 mph) (using the throttle position signal from the EEC)
Range Function
In the 4WD Low Range, the transfer case electromechanical clutch locks the front and rear driveshafts for maximum 4WD traction. The transfer case motor also rotates the shift cam to move the reduction fork to the 4WD low range position. This low range shift is accomplished through a planetary gear set which changes the torque to the driveshaft from 1:1 to 2.48:1 ratio.
In the 4WD High Range, the GEM locks the front and the rear driveshafts for maximum 4WD traction. This position is not meant for use on dry or merely wet pavement. It is intended for off-road or severe winter weather use only.
