Classic/Antique Car Repair: 67cadillac, hand vacuum pump, vacuum modulator

Question
my car is shifting at a high rpm the tranny is not slipping there is enough fuild in it is there something clogged

Answer
Either of two things can cause this. First is the vacuum modulator that reads engine intake manifold vacuum to determine shift points for the transmission. There is a vacuum line from the intake manifold to the modulator and that line can be disconnected or rotted through. The modulator can be checked by connecting a hand vacuum pump to it. It should hold 20" of vacuum. If the modulator and the vacuum connections are ok the detent switch located at the carburetor could be stuck in the downshift position. The easy test for this is to disconnect the wiring from the switch and road test the car. If it shifts normally the switch is defective or out of adjustment. The last is the governor inside the transmission sticking and this will require surgery. The governor can be removed without removing the transmission on this car.