Transmissions: Automatic Transmissions: Hydraulic system & controls

Hydraulic system components	The hydraulic system comprises a crescent type gear pump, a centrifugally operated hydraulic governor and a control valve body assembly.
Spool valves	The valve body contains spool valves which can be positioned manually or by hydraulic pressure or by springs.
Regulating or flow control valves	Spool valves can be regulating valves or flow control valves. Regulating valves regulate fluid pressure in the system.
Control valves	Control valves are simple 'gate' type valves which either open or close off a circuit with no alteration in pressure.
Orifices	Orifices can be used in hydraulic circuits to restrict fluid flow for timing purposes or to prevent valve fluctuations.

Topic	Summary