Ford USA

Automatic all wheel drive system. Same as Ford Maverick in Europe.

locking center differential activated by a switch on the dashboard.6 The AWD system normally sends most of the power from the engine to the front wheels. If slipping is detected at the front, more power will be sent to the rear wheels in a fraction of a second. The four wheel drive system was a newer version of Ford's "Control Trac" 4x4 system, dubbed the Control Trac II 4WD in the Escape. This system allowed the front wheels to receive 100% of the torque until a slip was detected. Using a Rotary Blade Coupling, the rear wheels could be sent up to 100% of the power in fractions of a second. When switching the system from "Auto" to "On," the front and rear axles are locked at a 50/50 split; the reaction time necessary to engage the rear wheels is reduced via an integrated bypass clutch.

Figure: ford escape first generation 4x4 logo (27KB)

Figure: ford escape first generation 4x4 switch (60KB)

Two wheel drive standard, optional Ford's Control Trac selectable all wheel drive (2H - Auto4wd - 4H - 4L). In Auto4wd mode the behaviour is similar to the automatic all wheel drive - the vehicle is normally rear-wheel drive. Torque is transferred to the front axle via an electro-magnetic clutch when slipping occurs. In 4H mode the clutch is fully locked and the front and rear driveshafts turn at the same speed. Optional locking rear differential.

Figure: Ford Expedition (2003) vacuum-disconnected front hubs for 2wd mode (16KB)

See http://en.wikipedia.org/wiki/Control_Trac

Full-time all wheel drive with central differential locking and low gear.

• 4X4 AUTO - Power to all four wheels; used for normal street and highway driving.
• 4X4 HIGH (4WD High) - Used for extra traction such as in snow or icy roads or in off-road situations. Not intended for use on dry pavement.
• 4X4 LOW (4WD Low) - Uses extra gearing to provide maximum power to all four wheels. Intended only for off-road applications such as deep sand, steep grades or pulling heavy objects. The accelerator pedal is less sensitive than in 4X4 HIGH (4WD High) range. This is to improve vehicle control when operating in very rough terrain. 4X4 LOW (4WD Low) will not engage while the vehicle is moving; this is normal and should be no reason for concern

source: Ford Explorer III User Manual