2008 Ford Expedition Owner Guide 1st Printing - Page 228

Tires, Wheels and Loading VEHICLE CHARACTERISTICS 4WD and AWD Systems (if equipped) A vehicle equipped with AWD or 4WD (when selected) has the ability to use all four wheels to power itself. This increases traction which may enable you to safely drive over terrain and road conditions that a conventional two-wheel drive vehicle cannot. Power is supplied to all four wheels through a transfer case or power transfer unit. 4WD vehicles allow you to select different drive modes as necessary. Information on transfer case operation and shifting procedures can be found in the Driving chapter. Information on transfer case maintenance can be found in the Maintenance and Specifications chapter. You should become thoroughly familiar with this information before you operate your vehicle. On some 4WD models, the initial shift from two-wheel drive to 4WD while the vehicle is moving can cause a momentary clunk and ratcheting sound. These sounds are normal as the front drivetrain comes up to speed and is not cause for concern. Do not become overconfident in the ability of 4WD and AWD vehicles. Although a 4WD or AWD vehicle may accelerate better than two-wheel drive vehicle in low traction situations, it won't stop any faster than two-wheel drive vehicles. Always drive at a safe speed. 228 2008 Expedition (exd) Owners Guide (post-2002-fmt) USA (fus)