top of page

Understanding the Overrun Clutch

What does an overrun clutch do?

An overrun clutch keeps the rotational momentum of your tractor mower from “pushing” your tractor after the clutch pedal is pushed in.

Overrun clutches are a “must” if your tractor does not have a “live” PTO --- as is typical with Yanmars.

The danger of not having an overrun clutch.

Let us say you do not have an over run clutch and you are out mowing.

When you press your clutch pedal, the mower will continue to spin. This is due to the rotational momentum of the blades. You may be surprised just how much momentum is stored in the spinning mower.

Because there is a connection between the transmission and the PTO --- this momentum continues to spin the transmission gears. This keeps the tractor moving forward.

Many people have ordered overrun clutches after crashing into cars, trees, garage doors, and even people.

Think about it this way --- you press the clutch and the tractor keeps moving. Talk about dangerous!

Even if you press the brakes, it will take several seconds to stop. Plus, this is very hard on your tractor’s transmission due to the low gearing.

You will keep moving forward until one of two things happens --- (1.) you shift the PTO or transmission into neutral, or (2.) the mower stops spinning.

How an over run clutch works.

An over running clutch acts like a ratchet.

Think of it this way --- you can turn hard on a ratchet one way to tighten a bolt. Then it spins easily when you turn it the other way. It is the same thing with the over running clutch.

The overrunning clutch allows the tractor to apply power to spin the mower, but the mower cannot apply its momentum back to spin the transmission. When you install an over running clutch, you can depress the clutch and the tractor will instantly stop but the mower will eventually spin to a safe stop.