Automatic Transaxle - 4T65-E - Service, Diagnosis & Troubleshooting: Specifications Chevrolet Uplander I

Upshift Control and Torque Converter Clutch (TCC) 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.

Perform the following steps

1. Refer to the «Shift Speed»(ref-241713-S37446428692006081100000) table and choose a throttle position of 12 percent, 25 percent or 50 percent. 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 Commanded gear Slip speed Solenoid states
3. Place the gear selector 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 to 2 seconds of the commanded gear change.
6. Compare the shift speeds to the Shift Speed table. Refer to «Shift Speed»(ref-241713-S37446428692006081100000) . 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 through 6 to complete all throttle angles.
8. Check for TCC apply in THIRD and FOURTH gear. 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 Refer to «Torque Converter Diagnosis Procedure»(ref-241746-S00230985672006081100000) Refer to the «Shift Speed»(ref-241713-S37446428692006081100000) table for the correct TCC apply speeds. Lightly tap and release the brake pedal. The TCC will release on most applications.

Torque Converter Diagnosis Procedure

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 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 problem 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

Torque Converter Evaluation and Diagnosis

Replace the torque converter if any of the following conditions exist

1. External leaks appear in the hub weld area.
2. The converter hub is scored or damaged.
3. The converter pilot is broken, damaged or fits poorly into the crankshaft.
4. You discover steel particles after flushing the cooler and the cooler lines.
5. The pump is damaged or you discover steel particles in the converter.
6. 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.
7. The converter has an imbalance which cannot be corrected. Refer to «Flexplate/Torque Converter Vibration Test»(ref-241746-S06291019312006081100000) .
8. The converter is contaminated with engine coolant which contains antifreeze.
9. An internal failure occurs in the stator roller clutch.
10. You notice excessive end play.
11. Overheating produces heavy debris in the clutch.
12. 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 if you discover any of the following symptoms

1. The oil has an odor or the oil is discolored, if there are no metal or clutch facing particles present.
2. The threads in one or more of the converter bolt holes are damaged. Correct the condition with a new thread insert.
3. 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.
4. 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.

Torque Converter Replacement Guide

Torque Converter Replacement Guide

Indexing Torque Converter

To determine and correct a torque converter vibration, the following procedure may have to be performed several times to achieve the best possible torque converter to flywheel balance.

1. Raise and suitably support the vehicle. Refer to «Lifting and Jacking the Vehicle»(ref-241684-S36257494482006081100000) in General Information.
2. Rotate the torque converter one bolt position.
3. Align the torque converter hub (2) in the engine crankshaft (3) and install the torque converter to flywheel bolts. Refer to «Flywheel to Torque Converter Bolt Replacement»(ref-241713-S03548337862006081100000) .
4. Lower the vehicle.
5. With the engine at idle speed and the transmission in PARK or NEUTRAL, observe the vibration. Refer to «Noise and Vibration Analysis»(ref-241746-S18818458672006081100000) . Repeat this procedure until you obtain the best possible balance.
6. Install the transmission converter cover bolts and the cover. Refer to «Torque Converter Cover Replacement»(ref-241713-S24745979452006081100000) .

Harsh Torque Converter Clutch (TCC) Apply or Release

Harsh TCC Apply or Release

No Torque Converter Clutch (TCC) Apply

No TCC Apply

See also:
• Scan Tool Data List (3.5L)
• Scan Tool Data List (3.9L)