Propeller Shaft Phasing Description

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The propeller shaft is designed and built with the yoke lugs, or the ears, in-line with each other. This produces the smoothest running shaft possible. A propeller shaft that is designed with built-in yoke lugs in-line is known as in-phase. An out-of-phase propeller shaft often causes vibration. The propeller shaft generates vibration from speeding up and from slowing down each time that the universal joint spins around. The vibration is similar to a person snapping a rope and watching the wave reaction flow to the end. An in-phase propeller shaft is similar to 2 persons snapping a rope at the same time and watching the waves meet and cancel each other. Cancelling the vibration produces a smooth flow of power in the drive line. All splined shaft slip yokes are keyed in order to ensure proper phasing.