[wagonman76]

My cars have a pin in the data connector connected to the TCC lockup solenoid wiring. Not sure about the cars of today, if it is that simple. But at worst you could get a wiring diagram and run your own wire. But also on my cars, the difference is night and day whether the TCC is locked or not. Newer cars seem to be much smoother.

But I agree, best way is to watch the tach if you have one. Once you are familiar with what you are identifying, eventually you'll probably be able to just go by feel.