Operation and maintenance manual

Section 120-0010
23
SM 2124 Rev 3 8-03
Retarder
The retarder is engaged when the bottom of the switch is
pressed and provided that the transmission 'Stop' warning
light is OUT and the transmission is in 'lockup'. To
disengage retarder, press the top of the switch. On TA40
machines, the retarder switch is incorporated in the brake
pedal. The first 7° of pedal travel engages the retarder,
provided that the transmission 'Stop' warning light is OUT
and the transmission is in 'lockup'. Further depression of
pedal applies service brakes. To disengage retarder,
release brake pedal. A warning light illuminates on the
dash to indicate when retarder is applied.
The retarder is used to apply a continuous braking force
to hold the truck to a safe steady speed when descending
grades, to reduce the need for service brake applications,
thus reducing service brake wear and preventing
overheating. The retarder may be used anytime to slow
down. If additional braking is required apply the service
brakes. The retarder is not meant for bringing the vehicle
to a halt, or for sudden deceleration - the service brakes
should be employed for this purpose.
Before the vehicle starts down the grade, release
accelerator, slow the vehicle with the service brakes,
select the required gear, and apply the retarder. For
maximum retardation, oil circulation and cooling, the
vehicle downgrade speed (retarder applied) in the gear
selected should be high enough to keep the engine
operating at governed speed. Generally the gear used to
ascend a grade is also correct for its descent. If the rate
of descent is too slow, the transmission should be
upshifted to the next highest gear. If the rate of descent
is too fast, the service brakes should be applied and the
transmission shifted into a lower gear which will allow a
safe descent and efficient retarder operation.
Frequent use of the retarder will result in higher transmission
oil temperatures. Therefore, the oil temperature gauge
should be checked frequently. During normal operation
the gauge should read in the green zone. However, during
retarder operation the gauge can read in the yellow zone.
Provided the vehicle is not in an overspeed condition, the
transmission 'Stop' warning light will illuminate when the
1
1 2
2
R
G
TCU
U
Bat
Gnd
P (power supply)
C (chassis)
Actuator / Sensor
8.1 Actuator:
8.2 Cable:
open circuit: R
12
≈ R
1G
≈ R
2G
≈∞
short cut to ground: R
12
≈ R; R
1G
≈ 0, R
2G
≈ R or R
1G
≈ R, R
2G
≈ 0 (for s.c. to ground, G is connected to
vehicle ground)
short cut to battery: R
12
≈ R; R
1G
≈ 0, R
2G
≈ R or R
1G
≈ R, R
2G
≈ 0 (for s.c. to battery, G is connected to
battery voltage)
open circuit: R
12
≈ R
1P
≈ R
1C
≈ R
2P
≈ R
2C
≈∞
short cut to ground: R
12
≈ 0; R
1C
≈ R
2C
≈ 0, R
1P
≈ R
2P
≈∞
short cut to battery: R
12
≈ 0, R
1C
≈ R
2C
≈∞,R
1P
≈ R
2P
≈ 0
Fig. 8 - Measuring Resistance at Actuator/Sensors and Cable
Transmission - Transmission and Mounting