PTO grinding

Fri Jun 20, 2014 10:42 am

Okay, time to take the denial stage head on...

The PTO on my '53 Cub just sits there and grinds 8 times out of 10 that I put it in gear. On the 9th try it will run for a few seconds then start grinding. On the 10th, it will hold and run the sickle mower.

What are the odds that this can be remedied with a new shift collar?

Or, should I just resign myself to having to do ANOTHER rear split to replace the transmission input shaft? At least the hood doesn't have to come off for that one. I just got done doing the front main engine seal.

Re: PTO grinding

Fri Jun 20, 2014 11:08 am

Did this just start happening, Matt? Has to be one of several things:

1. Main Shaft front seal retainer is installed incorrectly, allowing the shaft to drift forward, opening too much space between main shaft and PTO...Collar won't cover. Requires a split.
2. PTO shaft is a staked bearing version, and the shaft has drifted rearward. Doesn't require a split, but requires taking the PTO shaft out from the rear to remedy.
3. PTO shifter pin is worn from trying to hold the collar together on the shafts. This would cause the collar to not move forward enough to engage. Does not require a split to fix.

If it is engaging sometimes and not engaging other times, I suspect that it is #1 or #2.

Take the fill plug out of the top of the tranny and shine a light down in there. The gap between PTO and main shaft should be less than 1/4" for sure. That will tell the tale...


Re: PTO grinding

Fri Jun 20, 2014 12:27 pm

I suspect that it's been doing this a while. I've only had opportunity to start the PTO a handful of times since I've owned it.

Mostly I've avoided pulling the fill plug in dread of what I'll find. I bought this Cub knowing full well that most of the major seals needed replacement, and I've had a lot of fun pulling it apart every which way from Sunday, but I'd like to use it for a change, you know?

I have already had it apart to replace the transmission input shaft seal, and at that time I checked for movement on the input shaft. It was rock solid, and I made sure that the retainer was installed the correct way before buttoning it back up...

Odds are being a '53 it has the staked bearing, but the rear shaft doesn't look like it's slid back any.

What I'm hoping is the shift collar and maybe the pin are wore, but my guess is that the splines are rounded off on the input shaft too.

Re: PTO grinding

Fri Jun 20, 2014 1:09 pm

Your fears are well founded. If it has been grinding much at all, those splines are likely worn. This is a weak spot in the design of the Cub. There is not much in the way of good flat mating of the two surfaces before the rounded ends of the splines on the shaft. The pin is likely worn, too. One thing to try is to take the guide off or try to push it slightly rearward and fasten down again. This should give the shifter a bit more "throw" and help push the collar further forward on the shaft. This is a temporary fix, however.


Re: PTO grinding

Fri Jun 20, 2014 3:50 pm

Matt, Really not much in pulling one apart and rebuilding it….I've done a couple and its just a couple hour job….If that….Good instructions in the how to, right down to dangling a small light thru the tran hole ….Waiting on parts is the worst part….Good luck….Dave

Re: PTO grinding

Fri Jun 20, 2014 4:12 pm

The main transmission shaft has to stop turning before you engage the PTO. Other wise there will be grinding when you attempt to engage the PTO.

On my Cub I have to depress the clutch, then wait until every thing stops moving, takes a couple seconds, then I can shift gears or engage the PTO.

Suspect you are also having a grinding problem when I put the tractor in gear. This indicates a clutch or pressure plate problem.