3-16
Controls and Operating
Retarder Operation
Before the machine crests the top of a grade and starts down, the operator
should slow the machine with the service brakes and downshift to the gear range
which would be used to ascend the grade. The retarder should be applied before
starting the descent. Machine downgrade speed (with the retarder applied as
required) in the gear range selected should be high enough to keep the engine
operating at governed speed with the throttle closed (operator's foot off the
accelerator pedal). This will ensure maximum oil circulation and cooling. If the
rate of descent is too slow, the transmission should be upshifted to the next
highest gear range. If the rate of descent is too fast, the gear range selected is
too high and the operator must slow the machine by using the service brakes,
then downshift into a lower gear range which will allow a safe descent and
efficient retarder operation.
Great care should be used if applying the retarder when road
surfaces are slippery. Retarder braking effect will occur only at
the driving axle and could make vehicle control difficult.
Oil Temperature - Disc Brake
The disc brake hydraulic temperature warning light on the instrument panel will
illuminate and an electric horn will sound if the oil flowing through the disc brake
assemblies overheats. If alarm is activated, reduce downgrade travel speed. If
the trouble persists, stop the machine and have the fault corrected.
Oil Temperature - Transmission
During normal operation the transmission oil temperature gauge should read in
the green zone. However, during transmission retarder operation oil temperature
can enter the yellow 'RETARDER ON' zone but should not enter the red zone. Do
not allow the temperature to stay at or near the top of the yellow zone for more
than 3 minutes. Reduce downgrade travel speed to avoid the oil overheating and
possible damage to the transmission.
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