The hydraulic system comprises a crescent type gear pump, a centrifugally operated hydraulic governor and a control valve body assembly which regulates the pressure and directs fluid to the appropriate transmission components.
The pump is driven by tangs on the converter spout and is in operation whenever the engine is running.
It supplies all the hydraulic requirements of the transmission during operation.
The governor is driven by the transmission output shaft and provides a varying hydraulic pressure according to vehicle speed.
This variable pressure is used by the valve body as one of the required inputs to control upshifts and downshifts.
The valve body contains all the valves required for control of the transmission at all stages of operation.
They are mostly spool type valves but disc and ball check valves are also used.
The cylindrical spool valves have a number of distinguishing features.
The lands are the raised portions of the valve while the reduced diameter between each pair of lands is referred to as a valley.
The face of each land is machined square and sharp to the land diameter and some valves may have a stem or extension on one end to locate a regulating or return spring or to limit valve travel.
The sharp corners on the lands prevent the entry of dirt particles and also give the valve a self-cleaning action as it moves back and forth in the bore.
As there is only a very small clearance between the lands and the bore for each valve, they must be handled with care to avoid possible damage.
