| a power coupling for permitting a smooth start in any gear, consisting of two vaned rotors in a sealed casing filled with oil, such that one rotor, driven by the engine, moves the oil to drive the other rotor, which in turn drives the transmission. |
| fluid drive n. An automotive transmission coupling that provides a smooth start, consisting of two separate turbines that rotate on the same axis in a surrounding liquid, such that the turbine connected to the engine drives the turbine connected to the transmission. Also called fluid clutch. |