FORD 2010 F-550 v.1 - Manual (Page 216)

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.
WARNING: 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.
Tires, Wheels and Loading
216
2010 F-250/350/450/550 (f23)
Owners Guide, 1st Printing
USA (fus)