Ford 750 2009 Owner's Manual page 134

Driving
Note: Never use the differential lock at vehicle speeds above 25 mph
(40 km/h).
The differential lock and differential lock light will automatically
disengage at speeds above 25 mph (40 km/h). The differential lock will
remain off until either the vehicle is restarted or the differential lock
switch is turned off then back on.
Axle conversions
It is not recommended, or approved, for axle conversions to be
performed. However, it is understood that, on occasion, aftermarket
add-on axles are installed by others on the truck chassis which allow
operator control for weight transfer from other axles (i.e., air lift axles).
WARNING: When operating a loaded vehicle, the driver must
keep all adjustable axles on the ground at all times, supporting
their share of the vehicle's load. Failure to do so can overload other
axles, tires, wheels, springs, steering components, brakes and frames,
resulting in early component failure, loss of vehicle control, possible
property damage and personal injury.
TWO-SPEED REAR AXLE (IF EQUIPPED)
A two-speed rear axle allows the driver to select a LO range for greater
pulling power and a HI range for greater road speed and fuel economy.
These ranges can also be used to provide additional steps between
transmission shifts when driving on steep grades and/or fuel economy
may be factors.
Note: Do not shift between ranges when the speed control is on.
WARNING: Never shift a two-speed axle when descending a
steep grade as this may cause loss of vehicle control and result
in personal injury.
Axle shifting
Manual transmissions:
• To downshift, select the next lower gear, release and depress the
accelerator pedal rapidly, or while holding the accelerator pedal down,
release and engage the clutch rapidly. Note: The clutch method is
recommended when driving at slower speeds.
• To upshift, keep the accelerator pedal down, select the next higher
gear, release the accelerator and pause until the axle upshifts. Note:
De-clutch for smoother axle upshifts when driving at slower speeds.
134
2009 F-650/750 (f67)
Supplement
USA (fus)