Nobody likes annoying vibrations in their car and they can be hard to diagnose. Follow this Real Fix to see how a transmission vibration was diagnosed and repaired on this Cadillac DeVille.
Vehicle
2002 Cadillac DeVille 4.6L
Title
Transmission Vibrates, Replaced Torque Converter
Complaint
The customer states the transmission vibrates.
Cause
Confirmed the customer’s complaint and found the transmission vibrated. Performed a visual inspection of the automatic transmission fluid and found it was clean and at the proper level. Used a scan tool to monitor live data during a road test, accelerated to highway speeds, then maintained vehicle speed while lightly applying the brake to disengage the torque converter and observed the torque converter clutch parameter. Found the torque converter clutch slip speed parameter was erratic. Disconnected the automatic transmission wiring harness connector, used a multi-meter to measure the resistance of the torque converter clutch solenoid on the transmission side of the connector, and found the measured resistance was within specifications. Used the scan tool to command the torque converter clutch solenoid on while using the multi-meter to check for the presence of voltage and ground at the torque converter clutch solenoid circuits on the harness side of the connector, and found both were present. Removed the automatic transmission for further inspection, and found torque converter housing had traces of heat discoloration, which indicated the torque converter had overheated and caused the vibration. The result of these tests verified the torque converter was faulty.
Correction
Replaced the torque converter, performed a road test, and verified the vehicle operated properly. The check engine light did not illuminate and no fault codes returned.