In order to properly diagnose the Torque Converter Clutch (TCC) system, perform all of the electrical testing first. Then do the hydraulic testing.

The TCC is applied by fluid pressure, which is controlled by a solenoid inside of the automatic transmission assembly. The solenoid is energized by completing an electrical circuit through a combination of switches and sensors.

Functional Check Procedure

1. Install a tachometer or a Scan Tool .
2. Operate the vehicle until you reach the proper operating temperature.
3. Drive the vehicle at 80-88 km/h (50-55 mph) with a light throttle (road load).
4. Maintaining the throttle, lightly touch the brake pedal. Check for the release of the TCC and a slight increase in engine speed (RPM).
5. Release the brake. Slowly accelerate and check for a re-apply of the TCC and a slight decrease in engine speed (RPM).

Torque Converter Stator

The torque converter stator roller clutch can have one of two different types of malfunctions:

Condition A -- Poor Acceleration Low Speed

The car tends to have a poor acceleration from a standstill. At speeds above 50-55 km/h (30-35 mph), the car may act normal. If you note 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 (N), you can assume that the engine and exhaust system are normal. Checking for poor performance in DRIVE and REVERSE helps determine if the stator is freewheeling at all times.

Condition B -- Poor Acceleration High Speed

Engine RPM and car speed are limited or restricted at high speeds. Performance when accelerating from a standstill is normal. The engine may overheat. Visual examination of the converter may reveal a blue color from overheating.

If the converter has been removed, the stator roller clutch can be checked by inserting two fingers into the splined inner race of the roller clutch and try to turn the race in both directions. The inner race should turn freely clockwise, but the inner race should not turn or be very difficult to turn counterclockwise.

Noise

Torque converter whine usually is noticed when the vehicle is stopped and the transmission is in DRIVE or REVERSE. The noise increases when the engine RPM increases. The noise stops when the vehicle is moving or when the torque converter clutch is applied because both halves of the converter are turning at the same speed.

Perform a stall test to make sure the noise actually is coming from the converter:

1. Place a foot on the brake.
2. Put the gear selector in DRIVE.

Important: This noise should not be confused with the pump whine noise which is usually noticeable in PARK, NEUTRAL and all other gear ranges. Pump whine varies with pressure ranges.

3. Depress the accelerator to approximately 1200 RPM for no more than six seconds.

A torque converter noise increases under this load.

4. The torque converter should be replaced under any of the following conditions:

•	External leaks in the hub weld area

•	The converter hub is scored or damaged.

•	The converter pillar is broken or damaged or fits poorly into the crankshaft.

•	You find steel particles after flushing the cooler and cooler lines.

•	The pump is damaged or the steel particles are found in the converter.

•	The vehicle has TCC shudder and/or no TCC apply. Replace only after you have made all of the hydraulic and electrical diagnoses. (Converter clutch material may be glazed).

•	The converter has an imbalance which cannot be corrected. (Refer to the Converter Vibration Test Procedure).

•	The converter is contaminated with engine coolant containing antifreeze.

•	Internal failure of stator roller clutch

•	Excess end play.

•	Heavy clutch debris due to overheating (blue converter)

•	Steel particles or clutch lining material found in fluid filter or on magnet when no internal parts in the unit are worn or damaged - indicates that the lining material came from the converter.

5. The torque converter should not be replaced if any of the following conditions exist:

•	The oil has an odor, is discolored, and there is no evidence of metal or clutch facing particles.

•	The threads in one or more of the converter bolt holes are damaged. Correct with thread insert.

•	Transmission failure did not display evidence of damage or worn internal parts, steel particles or the clutch plate lining material in the unit and inside the fluid filter.

•	The vehicle has been exposed to high mileage (only). The exception may be where the torque converter clutch damper plate lining has seen excess wear by the vehicles operated in heavy and/or constant traffic, such as a taxi, deliver or police use.