In order to properly diagnose the Torque Converter Clutch
(TCC) system, perform the all electrical testing first and then perform the
hydraulic testing.
The Torque Converter Clutch (TCC) is applied by fluid pressure, which
is controlled by a solenoid valve. This solenoid valve is located on the side
of the valve body.
The solenoid valve is energized by completing an electrical circuit
through a combination of switches and sensors.
Functional Check Procedure
- Install a tachometer or a scan tool.
- Operate the vehicle until you have reached proper operating temperature.
- Drive the vehicle at 80-88 km/h (50-55 mph)
with a light throttle (road load).
- Maintaining throttle speed, lightly touch the brake pedal. Check
for the release of the TCC and a slight increase in engine speed.
- Release the brake and slowly accelerate. Check for a reapply of
the converter clutch and a slight decrease in engine speed.
Torque Converter Stator
The torque converter stator roller clutch can have two different malfunctions.
| • | The stator assembly freewheels in both directions. |
| • | The stator assembly remains locked up at all times. |
Poor Acceleration at Low Speed
If the stator is freewheeling at all times, the car tends to have poor
acceleration from a standstill. At speeds above 50-55 km/h (30-35 mph),
the car may act normally. For poor acceleration, you should first determine
that the exhaust system is not blocked, and the transmission is in First gear
when starting out.
If the engine freely accelerates to high RPM in Neutral, you can assume
that the engine and the exhaust system are normal. Check for poor performance
in Drive and Reverse to help determine if the stator is freewheeling at all
times.
Poor Acceleration at High Speed
If the stator is locked up at all times, performance is normal when
accelerating from a standstill. Engine RPM and car speed are limited or restricted
at high speeds.Visual examination of the converter may reveal a blue color
from overheating.
If the converter has been removed, you can check the stator roller clutch
by inserting two fingers into the splined inner race of the roller clutch
and trying to turn the race in both directions. You should be able to freely
turn the inner race clockwise, but you should have difficulty in moving the
inner race counterclockwise or you may be unable to move the race at all.
Noise
Important: Do not confuse this noise with pump whine noise, which is usually noticeable
in PARK, NEUTRAL and all other gear ranges. Pump whine will vary with line
pressure.
You may notice a torque converter whine when the vehicle is stopped
and the transmission is in DRIVE or REVERSE. This noise will increase as you
increase the engine RPM. The noise will stop when the vehicle is moving or
when you apply the torque converter clutch, because both halves of the converter
are turning at the same speed.
Perform a stall test to make sure the noise is actually coming from
the converter:
- Place your foot on the brake.
- Put the gear selector in DRIVE.
Notice: You may damage the transmission if you depress the accelerator for more
than 6 seconds.
- Depress the accelerator to approximately 1,200 RPM for no more
than six seconds.
A torque converter noise will increase under this load.
Replace the Torque Converter
Replace the torque converter under any of the following conditions:
| • | 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 the
cooler lines |
| • | The pump is damaged, or you discover steel particles in the converter |
| • | The vehicle has TCC shudder and/or no TCC apply. Replace 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 corrected. Refer
to the Flexplate/Torque Converter Vibration Test Procedure later in this section. |
| • | 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 no internal parts in the unit are worn
or damaged. This condition indicates 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 odor or the oil is discolored, even though metal
or clutch facing particles are not present. |
| • | The threads in one or more of the converter bolt holds are damaged.
Correct the condition with a thread insert. Refer to the Engine Mechanical
section. |
| • | Transmission failure did not display evidence of damaged or worn
internal parts, steel particles or clutch plate lining material in the unit
and inside the fluid filter. |
| | The vehicle has been exposed to high mileage only. An exception may
exist where the lining of the torque converter clutch dampener plate has seen
excess wear by vehicles operated in heavy and/or constant traffic, such as
taxi, delivery, or police use. |
