Some owners of 2008-2009 Cadillac CTS, SRX and STS vehicles equipped with the 6L50 automatic transmission may complain about erratic torque converter (TCC) operation or an illuminated MIL. Technicians may find DTCs P0751 and/or P0741 in the TCM as a history or active DTC.
This condition may be caused by de-bonding of the torque converter friction material. Typical symptoms of this condition include:
- Concern occurs on transmissions with less than 7.500 miles.
- Erratic TCC slip speed when monitored with a Tech 2 while driving. When TCC is applied, slip speed will vary from low (approximately 30 RPM) to high (approximately 150 RPM) to low and will not maintain a constant slip speed.
- Metallic (steel) debris in the oil pan. The amount of debris may vary from a very small amount to moderate and will usually be in the form of fine filings/flakes (not chunks).
If de-bond is suspected, remove the transmission to inspect the torque converter build date. This date will be stamped on the torque converter, engine side, near one of the mounting lugs and will be a Julian date. The suspect Julian date range is 15708 (157th day of 2008) to 22708 (227th day of 2008). If the torque converter build date is in this range, a final test is to remove the torque converter, engage a turbine shaft to the torque converter and turn the turbine shaft by hand. If the torque converter feels rough or gritty when turning the turbine shaft, the torque converter is the cause of the concern. The transmission should be disassembled and inspected. If there are signs of internal distress, contact the PQC for directions.
NOTE: Be sure to flush the cooler system following SI instructions for Transmission Fluid Cooler Flushing and Flow Check J 45096. Failure to properly flush the transmission cooling system could result in repeat transmission damage.