Transmission

[O'Donnell]

what is the electrical plug ,with 2 wires ,on the side of the transmission for on a 1972olds 98

[joe_padavano]

2 hours ago, O'Donnell said:

what is the electrical plug ,with 2 wires ,on the side of the transmission for on a 1972olds 98

 

Your trans is a TH400. The wires in the plug are in a "T" configuration. 

 

 

The terminal on the lower leg of the "T" is the wire that operates the electric solenoid for trans downshift.  A switch on the accelerator pedal under the dash  provides +12V on this terminal when you floor the throttle.

 

The terminal across the top of the "T" is a wire to operate the Transmission Controlled Spark system.  TCS is an early emissions control system that disabled distributor vacuum advance in lower gears as a way to reduce NOx emissions. A pressure switch in the trans grounds that terminal in all gears except third.  This operates a solenoid vacuum valve on the intake that cuts off vacuum advance to the distributor in the lower gears.

 

Do not confuse this emissions-era trans with the 1965-67 TH400 that used the second terminal for the switch pitch torque converter.  Your 1972 trans does NOT have that feature.

Edited March 1, 2018 by joe_padavano (see edit history)

[O'Donnell]

Thanks a bunch Joe, extremely informative.