The Hydraulic system is actually a complex maze of passages and tubes that transfer transmission fluid under high pressure to all other parts of the transmission and torque converter. The diagram here is a simple one culled from a 3-speed automatic from the ’60s. The newer systems are however much more complex and are combined with computerized electrical units and components. Transmission fluid serves a number of purposes including: gear shift control, general lubrication and transmission cooling. quite Unlike the engine, which uses oil predominantly for lubrication, every aspect of a transmission’s functions are dependent on a constant supply of fluid under pressure. This is not far from the human circulatory system (the fluid is even red) where even a few minutes of operation when there is a lack of pressure can be harmful or even fatal to the life of the transmission.
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