Have you read through the owner's manual on the operation of this system? Specifically page 169? There's a lot of good information in the often ignored owner's manual.
In the event that you don't have the owner's manual, below is a blurb from the service manual:
"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 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.
- 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)"
-Rod