Automatic Transmission - Allison (Troubleshooting): Specifications GMC Sierra 3500

Upshift Control and Torque Converter Clutch (TCC) Apply

The transmission control module (TCM) calculates the upshift points based on the throttle angle and the engine, turbine and output speed. When the TCM determines that conditions are met for a shift to occur, the TCM commands the shift, and controls A and B solenoid current to proper control clutch pressures during the shift.

Perform the following steps

1. Choose a throttle position of 10 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 Output shaft speed Commanded range Slip speed Solenoid states
3. Place the shift selector in DRIVE.
4. Using the chosen throttle angle, accelerate the vehicle. Hold the throttle steady.
5. As the transmission upshifts, note the vehicle speed when the shift occurs for each range change. There should be a noticeable shift feel or engine speed change within 1 to 2 seconds of the commanded range change.
6. Shift speeds may vary slightly due to transmission fluid temperature or hydraulic delays in responding to the 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. Inspect for TCC apply in SECOND, THIRD, FOURTH and FIFTH range. 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 inspect for DTCs. Refer to «Torque Converter Diagnosis Procedure»(ref-184229-S08282712112005082200000) . 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 through the converter flow valve by the F trim solenoid. The converter flow valve and the F trim solenoid are located inside the automatic transmission assembly.

Torque Converter Stator

The torque converter stator assembly 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 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 release of the converter clutch. Shudder should never occur after the TCC piston is fully applied.

If the shudder occurs while the TCC is applying, the condition could 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 may be causing the conditions to occur

1. Leaking turbine shaft seal rings
2. A restricted release orifice
3. Defective friction material on the TCC piston

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 (8.1L)»(ref-184229-S21516325112005082200000) or «Flexplate/Torque Converter Vibration Test (6.6L)»(ref-184229-S08077057992005082200000) .
8. The converter is contaminated with engine coolant which contains antifreeze.
9. An internal failure occurs in the stator race.
10. Overheating produces heavy debris in the clutch.
11. You discover steel particles or clutch lining material in the control main filter or suction filter, or on the magnets, 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, even though metal or clutch facing particles are not 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 in the control main filter or suction filter.

Flexplate/Torque Converter Vibration Test (8.1L)

To determine and correct a torque converter vibration, use the following general procedure to achieve the best possible torque converter-to-flywheel balance. Refer to Transmission Replacement (With 6.6L Engine) or Transmission Replacement (With 8.1L (L18) Engine) for detailed procedure steps as appropriate.

Scheme 602

1. Disconnect the battery.
2. Raise the vehicle. Refer to «Lifting and Jacking the Vehicle»(ref-184175-S17163319502005082200000) in General Information.
3. Remove the starter motor bolts and position the starter motor aside. Refer to «Starter Motor Replacement (4.3L Engine)»(ref-184144-S07911227652005082200000) or «Starter Motor Replacement (4.8L, 5.3L, and 6.0L Engines)»(ref-184144-S27615589722005082200000) or «Starter Motor Replacement (6.6L (LB7) Engine)»(ref-184144-S26643033962005082200000) or «Starter Motor Replacement (6.6L (LLY) Engine)»(ref-184144-S36072456772005082200000) or «Starter Motor Replacement (8.1L Engine)»(ref-184144-S42906435932005082200000) in Engine Electrical.
4. Remove the converter housing inspection cover.
5. Repeat this procedure until you obtain the best possible balance. Unless already removed, remove the starter motor bolts and position the starter motor aside. Refer to «Starter Motor Replacement (4.3L Engine)»(ref-184144-S07911227652005082200000) or «Starter Motor Replacement (4.8L, 5.3L, and 6.0L Engines)»(ref-184144-S27615589722005082200000) or «Starter Motor Replacement (6.6L (LB7) Engine)»(ref-184144-S26643033962005082200000) or «Starter Motor Replacement (6.6L (LLY) Engine)»(ref-184144-S36072456772005082200000) or «Starter Motor Replacement (8.1L Engine)»(ref-184144-S42906435932005082200000) in Engine Electrical. Remove the torque converter bolts. Rotate the torque converter one bolt position. NOTE: Refer to Fastener Notice in Cautions and Notices. Install the torque converter bolts. Tighten: Tighten the bolts to 60 N.m (44 lb ft). Install the starter motor and starter motor bolts. Refer to «Starter Motor Replacement (4.3L Engine)»(ref-184144-S07911227652005082200000) or «Starter Motor Replacement (4.8L, 5.3L, and 6.0L Engines)»(ref-184144-S27615589722005082200000) or «Starter Motor Replacement (6.6L (LB7) Engine)»(ref-184144-S26643033962005082200000) or «Starter Motor Replacement (6.6L (LLY) Engine)»(ref-184144-S36072456772005082200000) or «Starter Motor Replacement (8.1L Engine)»(ref-184144-S42906435932005082200000) in Engine Electrical. CAUTION: Refer to Battery Disconnect Caution in Cautions and Notices. Connect the battery. Start the vehicle and test for vibration again.
6. Disconnect the battery.
7. Raise the vehicle. Refer to «Lifting and Jacking the Vehicle»(ref-184175-S17163319502005082200000) in General Information.
8. Remove the starter motor bolts and position the starter motor aside. Refer to «Starter Motor Replacement (4.3L Engine)»(ref-184144-S07911227652005082200000) or «Starter Motor Replacement (4.8L, 5.3L, and 6.0L Engines)»(ref-184144-S27615589722005082200000) or «Starter Motor Replacement (6.6L (LB7) Engine)»(ref-184144-S26643033962005082200000) or «Starter Motor Replacement (6.6L (LLY) Engine)»(ref-184144-S36072456772005082200000) or «Starter Motor Replacement (8.1L Engine)»(ref-184144-S42906435932005082200000) in Engine Electrical.
9. Install the converter housing inspection cover.
10. Install the starter motor and starter motor bolts. Refer to «Starter Motor Replacement (4.3L Engine)»(ref-184144-S07911227652005082200000) or «Starter Motor Replacement (4.8L, 5.3L, and 6.0L Engines)»(ref-184144-S27615589722005082200000) or «Starter Motor Replacement (6.6L (LB7) Engine)»(ref-184144-S26643033962005082200000) or «Starter Motor Replacement (6.6L (LLY) Engine)»(ref-184144-S36072456772005082200000) or «Starter Motor Replacement (8.1L Engine)»(ref-184144-S42906435932005082200000) in Engine Electrical.
11. Lower the vehicle.
12. Connect the battery.

Flexplate/Torque Converter Vibration Test (6.6L)

To determine and correct a torque converter vibration, use the following general procedure to achieve the best possible torque converter-to-flywheel balance. Refer to Transmission Replacement (With 6.6L Engine) or Transmission Replacement (With 8.1L (L18) Engine) for detailed procedure steps.

Scheme 603

1. Disconnect the battery.
2. Raise the vehicle halfway. Refer to «Lifting and Jacking the Vehicle»(ref-184175-S17163319502005082200000) in General Information.
3. Remove the starter motor bolts and position the starter motor aside. Refer to «Starter Motor Replacement (4.3L Engine)»(ref-184144-S07911227652005082200000) or «Starter Motor Replacement (4.8L, 5.3L, and 6.0L Engines)»(ref-184144-S27615589722005082200000) or «Starter Motor Replacement (6.6L (LB7) Engine)»(ref-184144-S26643033962005082200000) or «Starter Motor Replacement (6.6L (LLY) Engine)»(ref-184144-S36072456772005082200000) or «Starter Motor Replacement (8.1L Engine)»(ref-184144-S42906435932005082200000) in Engine Electrical.
4. Repeat this procedure until you obtain the best possible balance. Unless already removed, remove the starter motor bolts and position the starter motor aside. Refer to «Starter Motor Replacement (4.3L Engine)»(ref-184144-S07911227652005082200000) or «Starter Motor Replacement (4.8L, 5.3L, and 6.0L Engines)»(ref-184144-S27615589722005082200000) or «Starter Motor Replacement (6.6L (LB7) Engine)»(ref-184144-S26643033962005082200000) or «Starter Motor Replacement (6.6L (LLY) Engine)»(ref-184144-S36072456772005082200000) or «Starter Motor Replacement (8.1L Engine)»(ref-184144-S42906435932005082200000) in Engine Electrical. Remove the torque converter bolts. Rotate the torque converter one bolt position. NOTE: Refer to Fastener Notice in Cautions and Notices. Install the torque converter bolts. Tighten: Tighten the bolts to 60 N.m (44 lb ft). Install the starter motor and starter motor bolts. Refer to «Starter Motor Replacement (4.3L Engine)»(ref-184144-S07911227652005082200000) or «Starter Motor Replacement (4.8L, 5.3L, and 6.0L Engines)»(ref-184144-S27615589722005082200000) or «Starter Motor Replacement (6.6L (LB7) Engine)»(ref-184144-S26643033962005082200000) or «Starter Motor Replacement (6.6L (LLY) Engine)»(ref-184144-S36072456772005082200000) or «Starter Motor Replacement (8.1L Engine)»(ref-184144-S42906435932005082200000) in Engine Electrical. CAUTION: Refer to Battery Disconnect Caution in Cautions and Notices. Connect the battery. Start the vehicle and test for vibration again.