Hydraulic power has a lot to do with how your transmission operates. There are some basic hydraulic components that keep your transmission running smoothly.
The transmission pump does exactly what you think – it pumps fluid. More specifically, the pump has an inner and outer gear, which draws fluid from the pan as the inner gear spins at the same speed as the engine. The pump supplies fluid to the torque converter, as well as the hydraulic system, which relies on fluid pressure to operate.
The torque converter seems simple in concept but is complex in application. It’s a fluid coupling – it converts to torque. The torque converter connects the engine to the transmission in terms of torque delivery, meaning it regulates and allows the constant spin of the engine to be transferred through the transmission in a useable form. One turbine spins faster in relation to the engine, causing more fluid pressure against the other turbine, which turns the transmission. There’s no direct mechanical transfer of motion; it all happens based on the motion of the fluid in the converter.
The valve body is like a hydraulic computer. Inputs in the form of different fluid pressures allow valves to open, which are loaded with different springs that take different amounts of pressure to operate. Those valves control when and where fluid travels, locking up or disengaging the clutches that either stop or release moving components.
These are your basic hydraulic components. Next, we’ll take a look at the mechanical components these hydraulics operate, and how that allows for different gear ratios to drive your car.