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You may notice a torque converter whine when the vehicle is stopped and the transmission is in Perform a stall test to make sure the noise is actually coming from the converter. 1. Bring the vehicle to a complete stop using the service brake. 2. Ensure that the engine is at low idle RPM. 3. Put the transmission in P, PARK. 4. Engage the P, PARK, range by slowly releasing the service brake. 5. Apply the emergency brake and/or parking brake, if present, and ensure it is properly engaged. 6. If the vehicle will be unoccupied with the engine running, chock the wheels and take any other steps necessary to keep the vehicle from moving. 7. Place your foot on the brake. 8. Place the range selector in DRIVE. 9. Depress the accelerator to approximately 1,200 RPM for no greater than 6 seconds. Listen for torque converter noise. A torque converter noise will increase under this load. 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 If the shudder occurs while the TCC is applying, the condition could be within the transmission or Something is not allowing the clutch to become fully engaged. Something is not allowing the clutch to release. usually noticeable in PARK, NEUTRAL and all other gear ranges. NOTE: You may damage the transmission if you depress the
2008 Chevrolet Silverado 1500 2008 TRANSMISSION Automatic Transmission - Allison - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
The clutch is releasing and applying at the same time. One of the following may be causing the conditions to occur: Leaking turbine shaft seal rings A restricted release orifice Defective friction material on the TCC piston IF SHUDDER OCCURS AFTER THE TCC HAS APPLIED As mentioned above, the TCC is not likely to slip after the TCC has been applied. Engine Once the TCC is applied, there is no torque converter, fluid coupling, assistance. Engine or Inspect the following components in order to avoid misdiagnosis of TCC shudder. An inspection Spark plugs Inspect for cracks, high resistance or a broken insulator. Plug wires Look in each end. If there is red ozone dust or a black carbon substance present, the wires Coil Inspect for black discoloration on the bottom of the coil. This indicates arcing while the Fuel injector IMPORTANT: If shudder occurs after the TCC has applied, most likely there is nothing wrong with the transmission.
2008 Chevrolet Silverado 1500 2008 TRANSMISSION Automatic Transmission - Allison - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
The filter may be plugged. Vacuum leak The engine will not get the correct amount of fuel. The mixture may run rich or lean Exhaust gas recirculation (EGR) valve The valve may let in too much or too little unburnable exhaust gas and could cause the Manifold absolute pressure (MAP) or mass air flow (MAF) sensor - possibly a vacuum leak The engine will not receive the correct amount of fuel for proper engine operation. Carbon on the intake valves Carbon restricts the proper flow of air/fuel mixture into the cylinders. Flat cam Valves do not open far enough to let the proper fuel/air mixture into the cylinders. Oxygen sensor This sensor may command the engine rich or lean for too long. Fuel pressure Fuel pressure may be too low. Engine mounts Vibration of the mounts can be multiplied by TCC engagement. Axle joints Inspect for vibration. Throttle position (TP) sensor
2008 Chevrolet Silverado 1500 2008 TRANSMISSION Automatic Transmission - Allison - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
The TCC apply and release depends on the TP sensor in many engines. If the TP sensor is Cylinder balance Malfunctioning piston rings or poorly sealed valves can cause low power in a cylinder. Fuel contamination Fuel contamination causes poor engine performance. TORQUE CONVERTER EVALUATION AND DIAGNOSIS Replace the torque converter if any of the following conditions exist: External leaks appear in the hub weld area The converter hub is scored or damaged The converter pilot is broken, damaged, or fits poorly into the crankshaft You discover steel particles after flushing the cooler and the cooler lines The pump is damaged, or you discover steel particles in the converter The vehicle has TCC shudder and/or no TCC apply Replace the torque converter only after all hydraulic and electrical diagnoses have been The converter has an imbalance which cannot be corrected Refer to Flexplate/Torque Converter Vibration Test. The converter is contaminated with engine coolant which contains antifreeze An internal failure occurs in the stator race Overheating produces heavy debris in the clutch You discover steel particles or clutch lining material in the control main filter or suction This condition indicates that lining material came from the converter. Do Not Replace the Torque Converter if you discover any of the following symptoms: The oil has an odor or the oil is discolored, even though metal or clutch facing particles are
2008 Chevrolet Silverado 1500 2008 TRANSMISSION Automatic Transmission - Allison - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
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