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When Dynamic Retarding is activated, an indicator
light in the Overhead Display will illuminate.
RETARDER CONTROL LEVER
The Retarder Control Lever (6, Figure 5-3) mounted
on the right side of the steering column can be used to
modulate retarding effort. The lever will command the
full range of retarding and will remain at a fixed position
when released.
a. When the lever is rotated to full "Up" (counter-
clockwise) position, it is in the "Off/No Retard"
position.
b. When the lever is rotated to full "Down" (clock-
wise) position, it is in the full "On/Retard" position.
c. For long downhill hauls, the lever may be posi-
tioned to provide a desired retarding effort, and it
will remain where it is positioned.
NOTE: The Retarder Control Lever must be ro-
tated back to the "Off" position before the truck
will resume the PROPEL mode of operation.
The lever and foot-operated Retarder/Service Brake
pedal can be used simultaneously or independently.
The Propulsion System Controller (PSC) will deter-
mine which device is requesting the most retarding
effort and apply that amount.
DYNAMIC RETARDER/SERVICE BRAKE PEDAL
The Dynamic Retarder/Service Brake Pedal (3, Figure
5-2) is a single, foot-operated pedal which controls
both retarding and service brake functions. The first
portion of pedal travel commands retarding effort
through a rotary potentiometer. The second portion of
pedal travel modulates service brake pressure directly
through a hydraulic valve. Thus, the operator must
first apply, and maintain, full dynamic retarding in order
to apply the service brakes. Releasing the pedal re-
turns the brake and retarder to the "off" position.
When the pedal is partially depressed, the dynamic
retarding is actuated. As the pedal is further de-
pressed, to where dynamic retarding is fully applied;
the service brakes (while maintaining full retarding) are
actuated through a hydraulic valve which modulates
pressure to the service brakes. Completely depress-
ing the pedal causes full application of both dy-
namic retarding AND the service brakes. An
indicator light in the overhead panel (B3, Figure 5-6)
will illuminate ), and an increase in pedal resistance
will be felt when the Service Brakes are applied.
N5-4
For normal truck operation, Dynamic Retarding (lever
or foot-operated pedal) should be used to slow and
control the speed of the truck.
Service brakes should be applied only when dynamic
retarding requires additional braking force to slow the
truck speed quickly, or when bringing the truck to a
complete stop.
ACCELERATOR (THROTTLE) PEDAL
The Accelerator Pedal (Throttle) Pedal (4, Figure 5-2)
is a foot-operated pedal which allows the operator to
control engine RPM, depending on pedal depression.
It is used by the operator to request torque from the
motors when in Forward or Reverse. In this mode, the
propulsion system controller commands the correct
engine speed for the power required. In Neutral, this
pedal controls engine speed directly.
Starting on a Grade With a Loaded Truck
Initial propulsion with a loaded truck should begin from
a level surface whenever possible, but when there are
circumstances where starting on a hill or grade cannot
be avoided, use the following procedure:
1. Fully depress the foot-operated retarder/service
brake pedal (DO NOT use retarder lever) to hold
the truck on the grade. With service brakes fully
applied, move the selector switch to a drive posi-
tion (Forward/Reverse) and increase engine
RPM with throttle pedal.
2. As engine RPM approaches maximum, and op-
erator senses propulsion effort working against
the brakes, release the brakes and let truck move-
ment start. Be sure to completely release the
foot-operated retarder/service brake pedal. As
truck speed increases above 3-5 MPH (5-8 KPH)
the Propulsion System Control (PSC) will drop
propulsion if the retarder is still applied.
Releasing and reapplying dynamic retarding dur-
ing a hill start operation will result in loss of
propulsion and, if truck speed is above 1-2 MPH,
application of retarding effort.
Operator Cab Controls
N05044
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