Hello,
There is a connector for the stick shift harness under the carpet on the side
of the console. If you remove the right side cover you should find the harness
under there. Look under the carpet once you have the cover off. The wires come from the O/D relay. They are blue and brown in the harness.

The red and yellow wires are the wires coming from the relay. The red goes to the fourth gear contact switch. The yellow goes to the O/D solenoid. The fourth gear switch provides ground so the relay will work only when you are in fourth.
If you remove the glove box and look behind the console just to the left of the glove box hole you will see a usually blue relay. This is the o/d relay.
Beware of the wires decaying inside the shifter itself. I just fixed that in my friend's turbo this weekend. I also had the resolder the relay circuit card. Wish you well.
Dave 82 242ti 280k mi.