I have played with manually shifting and letting the car shift itself. I have a turbo 350 with an adjustable modulator on it. The car went faster manually shifting. This is where it went south. Did my burnout and left the car in 2nd. Took off, saw the shift light on the tach, car shifted right on time, going, bleachers turning to a blur, going faster, shift light comes on, going, going, shift light still on, still on, pop ( huge puff of smoke). I didnt put the car in "D" for that run and I tore the torque converter up. It sounded like a maraca. Lesson learned......trust me!