Hydraulic System, Brakes

The transmission is controlled automatically by a hydraulic system. Hydraulic pressure is supplied by the transmission oil pump which is engine driven. Main line pressure is controlled by a pressure regulator valve train located in the pump and by a vacuum modulator which is connected to engine vacuum. The pressure regulator controls line pressure automatically, in response to a pressure signal from a modulator valve, in such a way that the torque requirements of the transmission clutches are met and proper shift spacing is obtained at all throttle openings.

To control line pressure properly, a modulator pressure is used which varies in the same manner as torque input to the transmission. Since the torque input to the clutches is the product of engine torque and converter ratio, modulator pressure must compensate for changes in either or both of these.

To meet these requirements, modulator pressure is regulated by engine vacuum, which is an indicator of engine torque and carburetor opening. It will decrease with an increase in vehicle speed to compensate for changing converter torque ratio.