Understanding TCC lockup logic (article on GM's approach) and how to modify it

[Daox]

Here is a very good article that outlines how GM's TCC (torque converter lockup) logic and design has changed over the years.

http://www.motor.com/magazine/pdfs/062006_07.pdf

The main reason for posting this is to learn how OEMs do it, so that we can modify our own transmissions to do what we want. Simply adding a TCC lockup switch in may not work. Its also very likely to cause a check engine light on more modern transmissions.

Has anyone installed a TCC lockup switch on a newer vehicle? Even my 1997 Sunfire has a PWM solenoid instead of an on/off solenoid. If I put a switch on, I expect a check engine light.

[mechman600]

The four speed auto on my Mazda Tribute (AKA Ford Escape) was an absolute slush box. The car was great except for the transmission and subsequent awful fuel economy. I attempted a manual TC lockup by simply wiring in a switch to ground the lockup solenoid. The solenoid always had 12V on one side and the ECU switched it on the ground side.

It would work for about 3 seconds, until the ECU realized what was going on and put it onto limp home mode, which required a key switch cycle to reset. I do not know whether it went by an unexpected changed in engine vs turbine speed or if it recognized a problem with the electrical circuit. Either way, I didn't try too hard to get it working properly.