PTO malfunction

[Ben B]

Well, I replaced my PTO shaft and clutch with the one out of my spare transmission and it is doing exactly the same thing. When I let out on the clutch the PTO spins up and then the shifter pushes forward in its guide, wedges against it, and starts grinding the PTO clutch against the transmission gear.

Is the shifter itself adjustable? It acts like it's not shifting far enough to stay engaged.

[Bob McCarty]

When you had it apart, did you check the pin that fits into the clutch? It's common that they wear a flat side and then do not move the clutch forward enough. There is no adjustment on the shifter. There is a dimple on the guide that fits on a bump on the tranny housing and prevents the guide from moving.

[Glen]

Hi,
What you described is probably the 2 splines grinding against the ends of each other, the splines in the PTO clutch, and the splines on the end of the clutch shaft.

[Ben B]

No, I didn't check the pin that fits into the shifter clutch. But, if I had to guess, I'd say that it's very possible that it has worn flat enough to allow it to travel backward to that point, especially if the PTO clutch has been pushing itself against it. I'll have to pull it back out again this evening and look at it.

And yes, the grinding is coming from the PTO clutch slipping off the transmission shaft just enough to allow the splines of each to grind.

[Ben B]

...and, I found this in another thread. viewtopic.php?t=100249 This was really the answer to the question I had. This tells me what I needed to know. My PTO has a serious driving force trying to disengage it constantly, and I knew that shouldn't be correct or it would have never lasted 67 years...

For those members that have worn pins, keep in mind that the slipping in and out of gear with the pto shifter usually doesn't wear the pin down like this, it's usually the worn splines on the end of the trans shaft that causes a continuous driving force to disengage. Sometimes the pto shaft splines are also worn and the sliding clutch hub wiggles adding to wear. Don't forget about the pto pilot bushing worn out too. A perfect pto assembly stays locked in with no reason to wear like that. My .02
Rick

I'm thankful to all the members on here who contribute, whether directly or indirectly! Thanks to you all for sharing your information with us! Now, I know what's wrong, the root cause, and what I have to do to fix it right!

Looks like I'm going to be going through my 56 transmission and get it ready to transplant my original one. (which I had planned to do anyway, just not during mowing season!)

[tmays]

Shouldn’t feel vibration in the shift lever with the pto engaged. If you do, then something is wrong and the pin that rides in the collar will wear in a relatively short time

[Ben B]

Here's what caused the malfunction: Shifter worn severely, probably about 60% worn through. And, the pilot bushing was worn just about slap out to the point that it is barely visible inside the shaft.

Now, is there any explanation for why this thing is so worn? Is it simply 67 years of work? Or, am I overworking it somehow?

[Scrivet]

First glad you found the immediate problem of the pin worn. I'll bet you look at the pins condition every time you have a PTO shaft out from now on.

.............Now, is there any explanation for why this thing is so worn? ..............

Think you already found that.....

...

.......... it's usually the worn splines on the end of the trans shaft that causes a continuous driving force to disengage. .......

The pin failure is not due to anything done wrong or being overworked in my opinion. It's a machine, things wear out, like pistons and rings, tires, throttle quadrants, brake linings, and splines on the end of the driveshaft........

The worn pin is most likely just a symptom though, not the real issue. Check the driveshaft splines over well before replacing the pin. Rounded splines will wreck another pin in short order.

[Ben B]

Thank you for the input. You were correct.

So, to temporarily correct the problem and get me back mowing again, I swapped out my 56 transmission because it has a much better pilot bushing in the main shaft, and because it is not busted and brazed like my original transmission is. Its PTO shifter has very little wear compared to my 50, so it makes me think it wasn't used much. It's splines also have more crisp edges on them. I will pick up seals this morning and this evening hopefully finish putting it all back together.

Now, my long term permanent solution is to do a total rebuild with another transmission case that I have, and use the good stuff out of the 50 transmission and order new parts to replace what is worn out. Looks like I will need a new main drive shaft for it, because the PTO splines are well rounded as you suggested earlier. It also has worn and rounded gears as compared to this 56's gears.

All this will actually help me in the long term. I had not planned to do a transmission rebuild, but after looking at it, that is really the smartest thing for me to do. Plus, it is fun to learn how all these things really work.