The hydraulic system of the Borg Warner 35 transmission has a number of regulating and control valves. They can be readily identified in a hydraulic circuit diagram.
This valve controls fluid pump output to maintain the required line pressure in the system. Line pressure is the highest pressure in the transmission and all other pressures are derived from line pressure.
This valve reduces line pressure to a low value for use in the torque converter, and in the cooler and lubrication circuits.
This valve is positioned manually by the driver operating the selector lever. It is a control valve which directs line pressure into particular circuits and exhausts fluid from other circuits when each range is selected.
This valve shares a common bore with the downshift or kickdown valve and both are influenced in their position and operation by the downshift cam, connected by a Bowden cable to the accelerator linkage. The throttle valve re-regulates line pressure to a value which is proportional to throttle opening.
The resultant throttle valve, or T.V. pressure, varies from zero at closed throttle to line pressure at full throttle. This pressure is supplied to the spring end of the shift valves to delay upshifts relative to throttle opening. The wider the throttle opening, the greater the T.V. pressure, and the higher the road speed will be before an upshift will occur.
T.V. pressure is also directed to the spring end of the primary regulating valve to progressively raise line pressure as the accelerator is depressed. This ensures the engaged servos or clutches are securely applied when high torque is being transmitted, and allows the pump to operate at lower pressures at other times. This reduces pumping losses and lowers fuel consumption.
