FORD 2015 F-550 v.2 - Manual (Page 166)

For 2WD vehicles and vehicles
equipped with a manual shift 4WD
system
E163191
Turn the control to ON.
E163170
Once the indicator light
illuminates in the information
display, both rear wheel axle
shafts will be locked together providing
added traction.
If the indicator does not come on, or the
indicator turns off while driving, one of the
following has occurred:
• The vehicle speed is too high.
• The left and right rear wheel speed
difference is too high during an
engagement attempt.
• The system has malfunctioned and is
accompanied by CHECK LOCKING
DIFFERENTIAL in the information
display. See your authorized Ford
dealer for assistance.
163
Super Duty (), enUSA
Rear Axle