Hummer H1 Service Manual page 325

5-126 Transmission/Transfer Case
Torque Converter Evaluation and Diagnosis
Replace the torque converter under any of the following condi-
tions:
• External leaks appear in the hub weld area.
• The converter hub is scored or damaged.
• The converter pilot is broken, damaged, or fits poorly
into the crankshaft.
• You discover steel particles after flushing the cooler and
cooler lines.
• The pump is damaged, or you discover steel particles in
the converter.
• The vehicle has TCC shudder and/or no TCC apply. Re-
place the torque converter only after all hydraulic and
electrical diagnoses have been made. The converter
clutch material may be glazed
• The converter has an imbalance which cannot be cor-
rected. Refer to Flywheel/Torque Converter Vibration
Test.
• The converter is contaminated with engine coolant
which contains antifreeze.
• An internal failure occurs in the stator roller clutch.
• You notice excessive end play.
• Overheating produces heavy debris in the clutch.
• You discover steel particles or clutch lining material in
the fluid filter or on the magnet, when not internal parts
in the unit are worn or damaged. This condition indi-
cates that lining material came from the converter.
Do Not Replace the Torque Converter
Do not replace the torque converter if you discover any of the
following symptoms:
• The oil has an oder or the fluid is discolored, even
though metal or clutch facing particles are not present.
• The threads in one or more of the converter bolt holes
are damaged. Correct the condition with a new J-nut.
• Transmission failure did not display evidence of dam-
aged or worn internal parts, steel particles or clutch plate
lining material in the unit and inside the fluid filter.
Torque Converter Clutch Shudder
The key to diagnosing Torque Converter Clutch shudder is to
note when it happens and under what conditions.
TCC shudder which is caused by the transmission should only
occur during the apply or the release of the converter clutch.
Shudder should never occur after the TCC plate is fully ap-
plied.
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If the shudder occurs while the TCC is applying, the problem
can be within the transmission or the torque converter. Some-
thing is causing one of the following conditions to occur:
• Something is not allowing the clutch to become fully
engaged.
• Something is not allowing the clutch to release.
• The clutch is releasing and applying at the same time.
One of the following conditions may be causing the problem to
occur:
• Leaking turbine shaft seals
• A restricted release orifice
• A distorted clutch or housing surface due to long con-
verter bolts
• Defective friction material on the TCC plate
If Shudder Occurs After TCC has Applied
If shudder occurs after the TCC has applied, most of the time
there is nothing wrong with the transmission!
As mentioned above, the TCC is not likely to slip after the
TCC has been applied. Engine problems may go unnoticed un-
der light throttle and load, but they may become noticeable af-
ter the TCC apply when going up a hill or accelerating. This is
due to the mechanical coupling between the engine and the
transmission.
Once TCC is applied, there is no torque converter assistance.
Engine or driveline vibrations could be unnoticeable before
TCC engagement.
Flywheel/Torque Converter Vibration Test
1. Start the engine.
2. With the engine at idle speed and the transmission in Park
or Neutral, observe the vibration.
3. Turn the key off.
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