Chrysler Repair: Transmission Code P0740, torque converter clutch, torque converter clutch circuit malfunction

Question
Roland,
I have a 2001 Chrysler Town & Country with a 3.8 liter engine and 105,000 miles on it that is giving off the following diagnostic codes (P0700 Transmission Control System Malfunction) and (P0740 Torque Converter Clutch Circuit Malfunction). I don’t have any noticeable drivability or shifting issues just that the service engine light has just illuminated. The vehicle has been regularly services including two transmission flushes (the last being at 100k). I don’t want to invest a lot of $$ in this car and based on these codes I'm sure it can be a multitude of problems but any insight you could provide would be appreciated.

Answer
Hi John,
The torque converter has a lock-up capability which comes into play when the vehicle is going  about 35 MPH or so and which you would notice as a slight slowing down of the engine as if the gear has shifted up about a 1/2 step. This produces a bit more economy of operation and less heating of the trans fluid and some braking action when you release the throttle. But it isn't crucial to the operation of the vehicle. It is hydraulically controlled by means of the solenoid on the torque converter clutch and solenoid pressure switches in the valve body that feed fluid to the clutch. It is possible that there is some dirt/malfunction in the valve body regarding the pistons that regulate the hydaulic pressure to the clutch on the torque converter so removal and repair/replacement of the valve body could re-establish the lock-up function. That would be a somewhat costly repair, done by dropping the oil pan and removing the valve body only, but much less costly than removal and replacement of the solenoid on the torque converter itself which would require removal of the transmission.
I would not recommend doing either at this time. Rather, wait until some more serious issue with the trans which requires overall rebuild at which time the torque converter problem could be simultaneously corrected would be prudent.
Roland
PS The 0700 merely is noticing that another specific code has been logged into the memory.