I worked on a guys cub a few years ago that the pto started popping out for him. I went and picked up the cub and brought it home. After I removed the pto assembly and looked inside, I could see the pto lever/shaft pin was worn off on his. This pic from TM shows the area that wears off,his was worn even worse.
I had an extra in my parts and installed it. I put everything back together and things seemed to work fine for me. I returned the cub to the owner. That lasted about a week. He called me and said it was popping out again
I went and picked up the cub again and brought it home. Took things apart and this time the pin was ground completely off Since this was my first pto problem of any kind, I was new at it and had to investigate further.
That's when I discovered the splines on the back of the tranny shaft. This meant I had to split the cub. Once things were apart, this is a pic of the bad splines on the shaft
I also had a replacement tranny shaft in my parts, so it was installed,along with a new pilot bushing in the end.http://www.tmtractor.com/new/pt/752fp.htm
along with a new pto lever/shaft from TMhttp://www.tmtractor.com/new/pt/752fp.htm
. You can see in this pic from TM how a good shaft should look
I put everything back together and things again worked fine. I returned the cub. The next year in the middle of the summer, the guy calls me to say it's popping out again
Now I'm ticked
and I suspect foul play. I went over to his house and drilled him about his technique. Come to find out, he was pushing the clutch pedal in and before the tranny stopped spinning, he would grind the pto into gear
, then when he finished mowing, he'd simply reach down while still moving and mowing and slide the lever out of gear
I then told him what he was doing wrong and he was the cause for the failures. I made him buy a new tranny shaft, another new pto lever/shaft and a new pto shaft and collar(http://www.tmtractor.com/new/pt/449-1fp.htm
). I also told him I would help him split the cub and show him how to put the new parts in. He saw first hand how things went together. I told him if he grinds the new stuff down, don't call me
I haven't heard a peep from him.
I said all that to say this: I'm beginning to think that the worn pin is a direct result from worm tranny splines, which is a direct result from operators not taking the time to take the pto out of gear. Each time you slip the shifter in or out of gear with things still spinning, you're wearing the tranny splines little by little, until eventually things need replaced.
Sorry for the long post,