Are you sure it’s a lock up chatter and not shifts chatter.


The lock up strategy has three mode, closed/slip/ and open. What you notice could be slip mode; 100 rpm drop is not much. What you need to monitor is PWM SOLENOID VAVLE STATUS, Closed duty cycle is greater then 80%, Slip 10 to 80%, Open is O%

The TCM can be commanding a slip mode, engaged, disengaged. Also lock up is only applied in 3rd, 4th and 5th gear.

Drive the car at above 55MPH at a steady throttle, monitor torque converter duty cycle and slippage RPM, a fully lock up converter will show 80% or greater DC. Fully locked
Slippage should be a negative number -100.

Do you know if the transmission has an update valve body, conductor plate and up dated soft ware to the TCM.. If not at lest change the torque converter solenoid, conductor plate and install an updated pressure regulator spring,