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PTO Gear box nuts loosening

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So I have a 712S from the mid 70's and it has the shuttle drive. I had a strange situation yesterday when I went to mow the law. The tractor would not move when I went into forward or reverse. I checked the PTO and the bell was spinning just fine but the shuttle drive on the opposite side was not moving. I noticed that the nut on the PTO shaft had loosened. Odd, but no problem. I tightened the nut and off I went cutting the lawn. About 15 minutes later, I lost blade rotation on the mower. When I checked the PTO bell, I noticed the nut that holds that on had loosened. More strangeness. So I tightened that and went on my way again. Well, that only lasted one pass as it loosened again. This next time I used Thread lock and let it sit overnight. Now I am perplexed with what could be causing the problem. Loose shaft bearing perhaps? Please share your thoughts?

Joe in Mass.

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The nut will have markings on the sides like little dents if it is suppsed to be drag/interference fit. Those nuts only get to be used a couple times before the drag factor has worn off. The alternatives are A new nut of same type, a nylock nut(for the same effect), or Loctite it in place. Loctite is a little more committed, but that may not be an issue.

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OK... all good advice. I went the loctite route since thats what i used on my new PTO Bell. Question still remains.... what could have caused nuts on both sides to loosen at roughly the same time. ?

I am concerned something internal is wobblying them loose. Or could be just paranoid. I'd rather not have to split the tractor again.

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How many threads are showing beyond the face of the nut? If it isn't the same amount each time - as in each time you retighten the nut you end up with more threads showing out of the nut, then there is something more going on.

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