"The Murray 51405MA Worm Gear is a high quality part designed to fit outdoor power equipment especially lawn mowers, and snow blowers. It is one of the integral components of the drive system that transfers power from the motor to other forms of mechanical devices due to the worm shape. In structural design, the gear features helical cut so that rotational movement is gradual and well... https://www.wholetoolbox.com/murray-51405ma-worm-gear