What does TCS stand for and what does it do. On my wiring diagram, a dark green wire comes from my temperature switch to this TCS relay which is mounted on the firewall. Then it goes to the TCS solenoid and then ? I am told it has something to do on the Tranny. Can any one help? "O" by the way thanks to a fellow Team Chevelle guy, I realized I forgot to say my car is a 70 ss 396 with cowl induction and turbo 400. Sorry.