Medium Duty Operator's Manual - Peterbilt Motors Company

STARTING AND OPERATING THE VEHICLE
• Dirt roads.
• Loose sand, mud, or other rough road conditions.
WARNING! Do not put the differential lock in
the LOCK position while the wheels are spinning
freely (slipping), you could lose control
of the vehicle or cause axle damage—you
could be injured. Switch to LOCK only when
the wheels are not spinning.
• Look ahead for wet, muddy, or icy patches on the
road, stop your vehicle and switch to LOCK ahead of
time.
WARNING! Do not operate the vehicle on dry
pavement with the differential locked. This
could lead to an injury accident. On dry pavement,
you will not be able to steer well with
the differential locked. Lock the differential
only when operating on surfaces with poor
traction, such as wet, slippery roads or loose
gravel.
OPERATING THE REAR/DRIVE AXLE
Inter–Axle Differential Lock Operation
WARNING! Do not use the inter-axle differential
lock when travelling downhill or at speeds
above 25 mph (40 km/h). When it is engaged
under these conditions, your vehicle will
exhibit “understeer” handling characteristics.
This “understeer” condition will cause
your vehicle to turn less quickly and more
steering effort will be required, which can
cause an injury accident.
To LOCK the inter-axle differential:
1. Anticipate when you might need increased traction,
slow down to a steady speed under 25 mph (40 km/h)
or stop the vehicle. Do not lock the inter-axle differential
while going down steep grades or traveling faster
than 25 mph, or while wheels are spinning or traction
is minimal; lock it before you encounter these conditions.
Medium Duty (R05/09) Y53-6008A – 125 –