K 3500 Truck 4WD V8-5.7L VIN R (1998)
Torque Converter Clutch: Initial Inspection and Diagnostic Overview
TORQUE CONVERTER CLUTCH DIAGNOSIS
The Torque Converter Clutch (TCC) is applied by fluid pressure, which is controlled by a PWM solenoid valve. This solenoid valve is located inside
of the automatic transmission assembly. The solenoid valve energizes or de-energizes by making or breaking an electrical circuit through a
combination of switches and sensors.
TORQUE CONVERTER STATOR
The torque converter stator roller clutch can have two different malfunctions.
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The stator assembly freewheels in both directions.
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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 a finger 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:
1. Place your foot on the brake.
2. Put the gear selector in DRIVE.
3. Depress the accelerator to approximately 1,200 RPM for no more than six seconds.
A torque converter noise will increase under this load.
NOTICE: You may damage the transmission if you depress the accelerator for more than six seconds.
