Hello. Torque Convertor does not lock up at highway speeds, above 50 M.P.H. in 4th gear. Someone suggested "jumping out" ALDL ports "A" and "F." after doing so, it worked fine. By the way, I changed "brake switch" at pedal. Brand new "ACDelco." The one with purple wire. There is another one also. TCC solenoid was changed-out maybe 5 or 6 years ago. I know there are two "pressure switches" in transmission for 3rd&4th gear, screwed to "valve body." For now, I will use jumper and take it easy. Over the winter, when car is in storage. I will pull pan down and trace back the wiring. Unless someone thinks it in the ECM? Let me know your thoughts, Thanks very much...