2004 Jeep Grand Cherokee Owner's Manual - Page 187

STARTING AND OPERATING 187 mode allows the front and rear wheels to rotate at different speeds which eliminates driveline binding and component wear that is normally associated with driving the vehicle in the 4 PART TIME position on dry hard surfaced roads. This feature provides the safety, security, and convenience of operating in 4 wheel drive at all times regardless of road conditions. When additional traction is required, the 4 PART TIME and 4LO positions can be used to lock the front and rear driveshafts together through the transfer case inter-axle differential and force the front and rear driveshafts to rotate at the same speed. This is accomplished by simply moving the shift lever to these positions. The 4 PART TIME and 4LO positions are intended for loose, slippery road surfaces only. Driving in the 4 PART TIME and 4LO positions on dry hard surfaced roads may cause increased tire wear and damage to driveline components. The PART TIME indicator light, located in the instrument panel, alerts the driver that a four wheel drive mode which locks the front and rear driveshafts together has been selected. This light illuminates when the transfer case is shifted to either the 4 PART TIME or 4LO positions. There is no light for the 2WD, 4 FULL TIME, or N (Neutral) positions. NOTE: Do not attempt to make a shift while only the front or rear wheels are spinning. The Selec-Trac transfer case is not equipped with a synchronizer and therefore the front and rear driveshaft speeds must be equal for the shift to take place. Shifting while only the front or rear wheels are spinning can cause damage to the transfer case. When operating your vehicle in 4LO, the engine speed is approximately three times that of the 4 ALL TIME position at a given road speed. Take care not to overspeed the engine and do not exceed 25 mph (40 km/h). 5