Automatic Transmission Diagnosis - 4L60-E: Specifications Chevrolet Silverado 2500

Torque Converter Clutch Solenoid Valve

The Torque Converter Clutch (TCC) solenoid valve is a normally open exhaust valve that is used to control torque converter clutch apply and release. When grounded (energized) by the PCM, the TCC solenoid valve stops converter signal oil from exhausting. This causes converter signal oil pressure to increase and move the TCC solenoid valve into the apply position.

Torque Converter Clutch Pulse Width Modulation Solenoid Valve

The Torque Converter Clutch Pulse Width Modulation (TCC PWM) solenoid valve controls the fluid acting on the converter clutch valve. The converter clutch valve controls the TCC apply and release. This solenoid is attached to the control valve body assembly within the transmission. The TCC PWM solenoid valve provides a smooth engagement of the torque converter clutch by operating during a duty cycle percent of on time.

Upshift Control & Torque Converter Clutch Apply

The PCM calculates the upshift points based primarily on two inputs: throttle angle and vehicle speed. When the PCM determines that conditions are met for a shift to occur, the PCM commands the shift by closing or opening the ground circuit for the appropriate solenoid.

1. Choose a throttle position of 10, 25 or 50 percent. See «SHIFT SPEED SPECIFICATIONS»(ref-139572-S31749840592002050200000) . All throttle angles shown should be tested to cover the normal driving range.
2. Monitor the following scan tool parameters: Throttle Angle Vehicle Speed Engine Speed Output Shaft Speed Commanded Gear Slip Speed Solenoid States
3. Place the gearshift lever in the Overdrive position.
4. Accelerate the vehicle using the chosen throttle angle. Hold the throttle steady.
5. As the transmission upshifts, note the vehicle speed when the shift occurs for each gear change. There should be a noticeable shift feel or engine speed change within 1-2 seconds of the commanded gear change.
6. Compare the shift speeds to the appropriate shift speed chart. See «SHIFT SPEED SPECIFICATIONS»(ref-139572-S31749840592002050200000) . Shift speeds may vary slightly due to transmission fluid temperature or hydraulic delays in responding to electronic controls. Note any harsh, soft or delayed shifts or slipping. Note any noise or vibration.
7. Repeat steps 1 - 6 to complete all throttle angles.
8. Check for TCC apply in 3rd and 4th gear. Typical apply speeds in 4th gear range from 45-55 MPH depending on engine size, engine type and axle ratio. Note the TCC apply point. When the TCC applies there should be a noticeable drop in engine speed and a drop in slip speed to below 100 RPM. If the TCC apply can not be detected, check for DTCs. Lightly tap and release the brake pedal. The TCC will release on most applications.

TORQUE CONVERTER DIAGNOSIS

Note. For additional torque converter information, see appropriate OVERHAUL article.

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 transmission assembly. The solenoid valve is controlled through a combination of computer controlled switches and sensors.

Torque Converter Stator

The torque converter stator roller clutch can have two different malfunctions

1. The stator assembly freewheels in both directions.
2. The stator assembly remains locked up at all times.

Torque Converter Clutch Shudder

The key to diagnosing Torque Converter Clutch (TCC) 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 applied.

If the shudder occurs while the TCC is applying, the problem can be within the transmission or the torque converter. Something is causing one of the following conditions to occur

1. Something is not allowing the clutch to become fully engaged.
2. Something is not allowing the clutch to release.
3. The clutch is releasing and applying at the same time.

One of the following conditions may be causing the condition to occur

1. Leaking turbine shaft seals.
2. A restricted release orifice.
3. A distorted clutch or housing surface due to long converter bolts.
4. Defective friction material on the TCC plate.