O'Donnell Posted March 1, 2018 Share Posted March 1, 2018 what is the electrical plug ,with 2 wires ,on the side of the transmission for on a 1972olds 98 Link to comment Share on other sites More sharing options...
joe_padavano Posted March 1, 2018 Share Posted March 1, 2018 (edited) 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) Link to comment Share on other sites More sharing options...
O'Donnell Posted March 3, 2018 Author Share Posted March 3, 2018 Thanks a bunch Joe, extremely informative. Link to comment Share on other sites More sharing options...
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