Medium Duty Operator's Manual - Peterbilt Motors Company

OPERATING THE REAR/DRIVE AXLE
STARTING AND OPERATING THE VEHICLE
Operating the Rear/Drive Axle
Introduction
This section covers the operation of your Rear/Drive Axle.
These instructions apply to the most common features of
drive axles. Refer to the manufacturer’s instructions for
further information on the operation of your axle.
If your vehicle is equipped with a Rockwell Tractech Nospin
single rear axle, the wheel differential lock feature
automatically engages and disengages. When one wheel
starts to spin on a slippery surface, this rear axle feature
engages to improve traction.
Interaxle Differential Lock
On vehicles with tandem rear axles, the interaxle differential
allows each axle to turn independently. Differential
action between the tandems relieves stress on the rear
axles and reduces tire wear. The interaxle differential lock
switch allows the operator to LOCK or UNLOCK the differential,
depending on road surface conditions.
When operating normally on paved, dry surfaces, keep
your truck's interaxle differential in the UNLOCK position.
SHIFT AT ANY SPEED EXCEPT
IF A WHEEL IS SPINNING
In the LOCK position, an air operated clutch positively
locks both sets of axles together, providing greater traction
on slippery road surfaces; however, steering around
corners and on dry pavement is more difficult. Continuous
operation on a paved, dry surface stresses the tandem
axles, possibly causing internal damage.
Use this feature only when driving on surfaces with poor
traction, such as wet slippery roads, heavy mud or snow,
or loose gravel. And do not use it when going downhill or
at speeds greater than 25 mph (40 km/h).
Lock the inter-axle differential when you encounter road
conditions such as these:
• Ice or snow — with or without tire chains.
– 124 – Y53-6008A Medium Duty (R05/09)