Ford 2002 Expedition Owner's Manual page 168

FOUR-WHEEL DRIVE (4WD) OPERATION (IF EQUIPPED)
For important information regarding safe operation of this type
of vehicle, see Preparing to drive your vehicle in this chapter.
When Four–wheel drive (4WD) is engaged, power is supplied to all four
wheels through a transfer case. 4WD power can be selected when
additional driving power is desired.
If equipped with the Electronic Shift 4WD System, and the
instrument panel control is moved to 4WD Low while the vehicle
is moving, the system will not engage and no damage will occur to
the 4WD system. Before 4WD Low can be engaged, the vehicle
must be at a complete stop with the brake pedal depressed and
the transmission in N (Neutral).
4H or 4L operation is not recommended on dry pavement. Doing
so could result in difficult disengagement of the transfer case,
damage to the transfer case, increased tire wear, decreased fuel
economy and difficulty turning.
Control-Trac automatic four-wheel drive system (if equipped)
Your 4x4 features the heavy-duty Control-Trac system which includes a
computer-operated transfer case. This unique system is interactive with
the road, continually monitoring and adjusting torque delivery to the
front and rear wheels to optimize vehicle control.
Positions of the Control-Trac system
The Control-Trac A4WD system
functions in three modes:
• A4WD position delivers power to
the rear axle. If the rear wheels
lose traction, power will be
automatically delivered to the
front axle to maintain traction
throughout the slippery condition.
• 4H position provides
mechanically locked four-wheel
drive power delivery to front and rear axles.
• 4L position provides mechanically locked four-wheel drive when above
average power at reduced speeds is required.
Driving
4H
A4WD
4L
167