Ford F-250 Owner's Manual page 298

Driving
will not engage while the vehicle is moving above 3 mph (5 km/h); this is
normal and should be no reason for concern. Refer to Shifting to/from
4L (4X4 low) for proper operation.
Shifting between 2H (4X2) and 4H (4X4 high)
Move the 4WD control between 2H (4X2) and 4H (4X4 high) at any
forward speed. The message center will display 4X4 SHIFT IN
PROGRESS during the system shift. "4X4 HIGH" will display in the
message center if 4H is selected and "4X2" will momentarily display in
the message center if 2H is selected.
If SHIFT DELAYED PULL FORWARD is displayed in the message
center during the mode shift, transfer case gear tooth blockage is
present. To alleviate this condition, place the transmission in a forward
gear and move the vehicle forward approximately 5 feet (2 meters) to
allow the transfer case to complete the mode shift.
Note: Momentarily releasing the accelerator pedal while performing a
shift will improve engagement/disengagement times.
Note: Do not perform this operation if the rear wheels are slipping.
Note: Some noise may be heard as the system shifts or engages; this is
normal.
Note: 4X4 high mode is not intended for use on dry pavement.
Shifting to/from 4L (4X4 low)
1. Bring the vehicle to a speed of 3 mph (5 km/h) or less.
2. Place the transmission in N (Neutral).
3. Move the 4WD control to the desired position.
The message center will display 4X4 SHIFT IN PROGRESS during the
shift. The message center will then display the system mode selected. If
any of the above shift conditions are not met, the shift will not occur and
the message center will display information guiding the driver through
the proper shifting procedures.
If SHIFT DELAYED PULL FORWARD is displayed in the message
center, transfer case gear tooth blockage is present. To alleviate this
condition, place the transmission in a forward gear, move the vehicle
forward approximately 5 feet (1.5 m), and shift the transmission back to
neutral to allow the transfer case to complete the range shift.
Note: Some noise may be heard as the system shifts or engages; this is
normal.
Note: 4x4 low mode is not intended for use on dry pavement.
298
2011 F-250/350/450/550 (f23)
Owners Guide, 3rd Printing
USA (fus)