fluid coupling

A fluid coupling, also known as a fluid drive or fluid clutch, is a type of coupling used in automobile mechanics that transmits torque through a fluid, typically oil. It consists of two vaned turbines facing each other, enclosed in a casing filled with oil. One turbine is connected to the engine's drive shaft, and the other to the transmission's driven shaft.12345

When the engine-driven turbine spins, it churns the oil, which then circulates and turns the second turbine. This fluid connection allows for smooth power transmission and prevents shocks and vibrations from reaching the transmission. At low engine speeds, the fluid coupling allows for slippage, enabling the car to idle while stationary. As the engine speed increases, slippage decreases, and the coupling acts almost like a solid connection. A hydraulic torque converter is similar but includes a stationary member that can increase torque, acting like an automatic transmission's gearbox and clutch.546