4l80e lockup from factory ecm


Car is finally back on the road after some time (life happens) and preliminarily I'm really pleased with the 4l80 swap.
I'm running it with one of the cheap manual control boxes available online for now, as a stopgap until I figure out what ultimately I'm doing with management on the car.
It's a pretty simple setup, one switched 12v source to the box will make it work, and then the transmission is in whatever gear you put it in.

There is also a lockup trigger wire, which needs a ground passed to it to activate. The factory tcc solenoid functions the same way, no? If so, could I not just jump that wire from the factory plug to the trigger wire from this manual control box, and retain the same lock/unlock function commanded by the ecm that I had with the 200? This would be nice both for driving normally, to avoid having to flip a switch and remember to flip it off again, as well as for commanding 3rd gear lockup on the track, as I have a multi disc converter for that purpose.

I see no reason why it wouldn't work just fine, am I missing anything? This 4l80 has a cable speedo drive grafted into the tail housing, so the ecm is getting a speed signal still.
Pin S is TCC in the 4L80E plug. should be able to tie it right to the stock TCC wiring.

Pin S is TCC in the 4L80E plug. should be able to tie it right to the stock TCC wiring.

View attachment 394403
looks like coming from black/tan in the factory plug to pin S is all it takes, then. Of course I have to get my speedometer signal back for that to actually do anything. I'll give this a try, I like the idea better than having to manually toggle lockup.