Hydraulic System, Brakes

The transmission is automatically controlled by a hydraulic system. Hydraulic pressure is supplied by the transmission oil pump, which is engine driven through the converter. Main line pressure is controlled by a pressure regulator valve train, see image, located in the pump housing. 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 are met and smooth shifts are 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 converter torque output 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. It is decreased by governor pressure with an increase in vehicle speed because converter torque ratio does the same.