PTO Runs when turned off

[ehoffmeyer]

Model 4035.
With both switches that control the activation of the PTO in the OFF position the PTO shaft still rotates slowly say about 100 RPM.

What causes this?
Thank you!
Eric

 

[shovelmike]

I would suppose the PTO is engaged and disengaged by a clutch actuated by an electromagnet. The clearances are close allowing the plates to touch somewhat, causing the rotation you observe. If anything is attached, it would not likely have enough force to turn it. There is no harm in the rotation, as the plates wear slightly it will probably no longer do so. For all I know mine may do the same, but the cover is in place when not utilized.

 

[ptsg]

So, your tractor has a clutch pack for the PTO. This means that you also have a solenoid valve and a switch to control it. Once you flip the switch to the On position, it will energize the solenoid valve and the valve will divert the fluid to the clutch pack. Which then engages the PTO.

With this style of PTO, when the switch is OFF, a spring inside the clutch pack will push the hub against a brake disc. So the PTO will stop.

I don't know how many hours you have on the tractor but it's not uncommon for this brake to wear out over time and basically the drag between the discs on the clutch pack will cause the PTO to rotate slowly like you're experiencing.

Another possible cause, would the be the spool on the solenoid valve is sticking and stays slightly open, which would send a small amount of fluid and tried to engage the clutch pack. But there is not enough pressure to engage fully.

If you hold a piece of 2x4" on the PTO shaft, it might just stop while you're applying pressure.

 

[skipperbrown]

My Kubota b2650 started doing this. The rear shaft will spin rather fast if the rear PTO shifter is selected but not engaged. However, if the PTO shifter is in the front PTO only position, The rear PTO shaft will be locked. When the rear shaft spins without the PTO engaged, you can easily stop the motion with your hand. After studying the shop manual, it appears there is an electric switch that is supposed to lock the PTO shaft when it is not engaged, but I have been unable to locate it to check for a loose connection or for a bad switch. I imagine your tractor has something similar to lock the shaft as it can be a safety issue if there is enough friction on the PTO shaft to spin a blade or tines. If your tractor is still under warranty, I'd ask the dealer to fix it.