Why Is an Overrunning Clutch Needed?

An overrunning clutch transmits torque in one direction only and permits the driven shaft of a machine to freewheel, or keep on rotating when the driver is stopped. On bicycles, such clutches permit the rider to coast without moving the pedals.

Do I need an overrunning clutch?

An overrunning clutch is often needed with a transmission PTO. Without it, the driven equipment (such as mower blades) will put a force on the PTO shaft, and then the transmission, due to inertia. The equipment will "drive" the tractor, and you will still move after using the tractor's transmission clutch.

What is the purpose of overrunning clutch in starter motor?

When you attempt to start your heavy machinery, you need the engine to start to turn freely as your engine attempts to run. The overrunning clutch in the starter drive makes this happen. So the overrunning clutch transmits torque in one direction but then freewheels in another direction.