FORD 2011 F-550 v.4 - Manual (Page 215)

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
vehicles. Although a 4WD 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.
How your vehicle differs from other vehicles
SUVs and trucks can differ from
some other vehicles in a few
noticeable ways. Your vehicle may
be:
• Higher – to allow higher load
carrying capacity and to allow it
to travel over rough terrain
without getting hung up or
damaging underbody components.
• Shorter – to give it the capability
to approach inclines and drive
over the crest of a hill without
getting hung up or damaging
underbody components. All other
things held equal, a shorter
wheelbase may make your vehicle
quicker to respond to steering inputs than a vehicle with a longer
wheelbase.
Tires, Wheels and Loading
215
2011 F-250/350/450/550 (f23)
Owners Guide, 4th Printing
USA (fus)