the tcc circiut consist of a relay and a soliniod in the tranny. the torque converter clutch locks up the torque convert so that it will not slip after you are up to operating temp. and speed.also the is a speed sensor .that tell the computer when to turn on the tcc.at 70 mph it should be reving 4000rpm if you have a three speed transmission.if you have a four speed i dont know what you should be reving.because i have a three speed automatic transmission.