Ford 2002 F650 Owner's Manual page 148

Driving
When split shifting, the axle shift control must stay UP in the
HIGH range until after any transmission lever movement.
A 2–speed axle should NEVER be shifted on a downgrade.
To downshift the axle from HIGH to LOW range, either the ring gear has
to speed up by one-third, or the wheels have to slow down by one-third
to allow for synchronization. When you are on a down grade, the wheels
will not slow down, but will tend to speed up. As a result, the ring gear
must be accelerated to synchronize speeds. You are however limited in
doing so by your engine governed speed, and may not be able to reach
synchronization to allow the shift to take place. If the shift is not
completed , the axle will be in neither HIGH nor LOW range and all
driveline retardation will be lost.
Ratio extender use
Low End
A 2–speed axle can be used as a ratio-extender when split shifting is not
necessary. For low end use, just shift the axle into the LOW to start out,
and shift to HIGH when the extra torque is no longer needed.
Transmission (5-speed)
2-speed Axle
High End
To use the 2–speed axle as a high end ratio-extender, stay in the LOW
range for normal upshifts and only shift the axle to HIGH on the freeway
for greater road speed.
Transmission (5-speed)
2-Speed Axle
DRIVING THROUGH WATER
Do not drive quickly through standing water, especially if the depth is
unknown. Traction or brake capability may be limited and if the ignition
system gets wet, your engine may stall. Water may also enter your
engine's air intake and severely damage your engine.
If driving through deep or standing water is unavoidable, proceed very
slowly. Never drive through water that is higher than the bottom of the
148
1st 1st 2nd
Axle
Low
1st 2nd
Low for Gradeability
3rd 4th
Axle High
3rd 4th
5th 6th
5th 6th
Speed
Axle
High