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TM 10-3930-671-24
7.2. Transmission Troubleshooting
Troubleshooting Techniques ......................................................... F-323
Powershift Transmissions ............................................................. F-323
Troubleshooting Guide ................................................................... F-323
Troubleshooting Procedures .......................................................... F-324
Converter Stall Procedure .............................................................. F-324
Troubleshooting Techniques
The following information is presented as an aid to
isolating and determining the specific problem area on a
transmission that is not functioning correctly.
When troubleshooting a "transmission" problem, it
should be kept in mind that the transmission is only the
central unit of a group of related powertrain components.
Proper operation of the transmission depends on the
condition
and
correct
functioning
of
the
other
components of the group. Therefore, to properly
diagnose a suspected problem in the transmission, it is
necessary to consider the transmission fluid, charging
pump, torque converter, transmission assembly, oil
cooler, filter, connecting lines and controls, including the
engine, as a complete system.
By analyzing the principles of operation together with the
information in this section, it should be possible to
identify and correct any malfunction which may occur in
the system.
Powershift Transmissions
Hydratork
(powershift
with
torque
converter)
transmission troubles fall into two general categories:
mechanical problems and hydraulic problems.
In addition to the mechanical components, all of which
must be in the proper condition and functioning correctly,
the correct functioning of the hydraulic circuit is most
important. Transmission fluid is the "life blood" of the
transmission. It must be supplied in an adequate
quantity and delivered to the system at the correct
pressures to ensure converter operation, to engage and
hold the clutches from slipping and to cool and lubricate
the working components.
Troubleshooting Guide
Refer to the following list of symptoms for the diagnosis
of typical transmission troubles.
Low Clutch Pressure
1.
Low transmission fluid level.
2.
Clutch pressure regulating valve spool stuck
open.
3.
Stuck inching valve.
4.
Inching/brake pedal not returned to full up
position.
5.
Defective or worn charging pump.
6.
Broken or worn clutch shaft or piston sealing
rings.
7.
Clutch piston bleed valve stuck open.
8.
Accumulator piston rings worn or broken.
Low Converter Out Pressure
Low Charging Pump Output
1.
Low fluid level.
2.
Suction screen has restriction.
3.
Defective or worn charging pump.
Overheating Unit Getting Too Hot
1.
Low fluid level.
2.
Worn charging pump.
3.
Worn oil sealing rings.
4.
Dirty oil cooler.
5.
Restriction in cooler line.
Noise In Converter
1.
Defective converter.
Loss of Power
1.
Low engine RPM @ converter stall. Tune
engine.
2.
Overheating See above items.
F-323
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