TH 700R4 TCC lockup wiring

[hatzie]

Originally Posted by Dannyboy1966

Lucky for me when the previous owner swapped my rig to a SM465 they were nice enough to tie the wiring up and leave it hanging under the hood by the brake master cylinder. So I have the brake and low vacuum switch, my concern was the internal wiring with it having 2 of the wires going to the ECM. So on the 1989 transmission I just use the A and B terminals and just forget about the C? Here is a close up of the internal wiring. Tell me if I have it right or correct me. Thanks Hatzie

Plug it all back in and drive it.

C is unused... D is the EGR ECM terminal. Your harness doesn't have a wire in C or D. That doesn't matter.

The picture is not needed. I have the uncompressed scans and a 50" 4K monitor.

[old blue 86]

So the brake switch and the low. vac. switch unlock the tcc but what locks it?

[Dannyboy1966]

Originally Posted by old blue 86

So the brake switch and the low. vac. switch unlock the tcc but what locks it?

To explain how it works, the brake switch, and low vac switch cut the power to the lock up solenoid inside the pan. Now a detailed description. In the trans there are 2 or 3 pressure switches and a solenoid. Power flows from the fuse panel, through the brake switch, then through the low vac switch and into the trans. If you throttle hard on the motor it's vacuum signal will decrease for for a brief time, causing the low vac switch to break the circuit and cut power to the lock up circuit until one of the switches inside the trans detects pressure in the 4th gear oil circuit. The brake switch works in a similar way, during braking or panic braking it cuts the power circuit and unlocks the torque converter, and remains unlocked until the 4th gear pressure switch detects pressure again. These same connections on the brake light switch also double as a cut off signal for the factory cruise control if equipped.