Service Manual

HYDROSTATIC DRIVE SYSTEM
6-20 GT Series Tractors Service Manual
6
The following procedures should be performed with the
vehicle drive wheels off the ground, then repeated under
normal operating conditions.
1. With the bypass valve open and the engine running,
slowly move the directional control (foot control) in
both forward and reverse directions 5 to 6 times; as
air is purged from the unit, the oil level will drop.
2. With the bypass valve in the closed position and the
engine running, slowly move the directional control
valve (foot control) in both forward and reverse
directions 5 to 6 times. After stopping the engine,
check the oil level and add oil as required.
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3. It may be necessary to repeat Steps 1 and 2 until all
the air is completely purged from the system. When
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speed purging is complete.
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drive applications, it is critical that it be purged from the
system.
These purge procedures should be implemented any
time a hydrostatic system has been opened to facilitate
maintenance or any additional oil has been added to the
system.
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systems.
The resulting symptoms in hydrostatic systems may be:
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2. Lack of power or drive after short term operation
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sion of oil
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port
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