Peterbilt Model 320 Operator's Manual after 8-07 - Peterbilt Motors ...

PART 4: CONTROLS AND DISPLAYS
When an engine brake is energized, the power-producing
diesel engine is converted into a power-absorbing air compressor
to retard the vehicle.
• The brake is energized whenever the driver’s foot is
completely removed from the accelerator pedal.
• The brake is deenergized during driving by pressure
on the accelerator pedal, and during shifting by depressing
the clutch pedal.
The ON/OFF toggle switch turns the system ON or OFF.
• In Caterpillar and Cummins L10-powered vehicles
equipped with a Jacobs Engine Brake, a second,
two-mode switch is incorporated in the instrument
panel. With this system, you can select either LOW
or HIGH retarding.
For more information on when and how to use the engine
brake in your vehicle, see the owner’s manual for the engine
brake that is included with your vehicle.
WARNING! Using the engine brake when operating
on surfaces with poor traction (such as
wet or icy, slippery roads or gravel) could cause
loss of control.
Interaxle Differential Lock Switch
Interaxle Differential Lock Switch
03029
The interaxle differential allows differential action between
the forward rear and the rear driving axles. The interaxle
differential lock switch allows the operator to LOCK or UN-
LOCK the differential. There is a guard over this switch to
prevent you from accidentally activating the lock.
R(08/07) Y53-6015 – 33 –