Control Trac Four–Wheel Drive System; Normal Characteristics; Sand - Ford Expedition 2003 Owner's Manual

Driving
Control Trac four–wheel drive system
When a four–wheel drive mode is selected, the Control Trac system uses
all four wheels to power the vehicle. This increases traction, enabling
you to 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. On
four–wheel drive vehicles, the
transfer case allows you to select
four–wheel drive when necessary.
Information on transfer case
operation and shifting procedures
can be found in this 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.

Normal characteristics

On some four–wheel drive models, the initial shift from two-wheel drive
to four–wheel drive while the vehicle is moving can cause some
momentary clunk and ratcheting sounds. This is the front drivetrain
coming up to speed and engaging the front wheels, and is not cause for
concern.

Sand

When driving over sand, try to keep all four wheels on the most solid
area of the trail. Avoid reducing the tire pressures but shift to a lower
gear and drive steadily through the terrain. Apply the accelerator slowly
and avoid spinning the wheels.
If you must reduce the tire pressure for whatever reason in sand, make
sure you re-inflate the tires as soon as possible.
Note: If your vehicle is equipped with the tire pressure monitoring
system, the system indocator light may illuminate depending on how
much air is released from your tires and/or how long you drive the
vehicle under these conditions.
Avoid excessive speed because vehicle momentum can work against you
and cause the vehicle to become stuck to the point that assistance may
be required from another vehicle. Remember, you may be able to back
out the way you came if you proceed with caution.
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