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  1. #1
    New Member
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    Jul 2013
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    Roebuck, SC
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    5103 John Deere

    Default PTO drive shaft sheering pins

    I have a John Deere 50 hp tractor and recently purchased a County Line (tractor supply brand) 5' rotary mower that sheered a couple of bolts where the rear U joint connects to the gear box shaft. I purchased a clutch for the shaft at gear box thinking that may help but it continues to sheer the bolt before the clutch at mower gear box. I was cutting grass which was not high and started the pto at low speed and gradually brought it up to 540 rpm. I never had that problem with the older Howze mower I had. Any thoughts?

  2. #2
    Elite Member bullbreaker's Avatar
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    Mar 2009
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    SW FLA 34120 ZIP
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    Kubota L3400 DT,John Deere GT 235,JD GENERATOR AC-G8010S-E

    Default Re: PTO drive shaft sheering pins

    What type(make) and grade are bolts being sheered ? Are they from same batch ?
    Do you still have old cutter around and did it have S-bolt init to try that one ? Just some thoughts.

    Boone
    2 CHRONICLES 7 : 14 (KJV)

  3. #3
    Gold Member idaho2's Avatar
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    Aug 2009
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    SW WA / North Idaho
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    Mahindra 5530 4WD Turbo - Gear,

    Default Re: PTO drive shaft sheering pins

    "I have a John Deere 50 hp tractor and recently purchased a County Line (tractor supply brand) 5' rotary mower that sheered a couple of bolts where the rear U joint connects to the gear box shaft."

    By chance did the retailer put 90wt in the gear box. Most often they arrive at the retailer minus oil. Have you checked it? Sounds like something is binding that is shearing your bolts. Could a leaking seal be the culprit from tall grass wrapping around the output shaft and damaged the seal.
    Just a thought.

    idaho2

  4. #4
    Super Star Member LD1's Avatar
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    Central Ohio
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    Kubota l3400

    Default Re: PTO drive shaft sheering pins

    1. Mower is grossly undersized and light duty for a 50HP tractor
    2. Is the clutch adjusted properly for the tractor/mower combination
    3. Are you still using grade 2 shear bolts? When converting to a slip clutch (that is set properly) use a stronger bolt
    ".........there is only one way to find out."
    "Ok, hold my beer and watch this.........."


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  5. #5
    Elite Member GManBart's Avatar
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    Dec 2012
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    2,766
    Location
    Belleville, MI
    Tractor
    Massey Ferguson 241, Massey Ferguson 2244 crawler

    Default Re: PTO drive shaft sheering pins

    If the slip clutch is set properly, I'd put a grade 5 or 7 bolt in it.

  6. #6
    Super Member RickB's Avatar
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    Sep 2000
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    Eastern NY
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    Case 885, Ford 4000

    Default Re: PTO drive shaft sheering pins

    A real rotary cutter will have a splined input shaft that won't rely on a bolt to transmit the torque from the clutch to the gearbox.
    Buy a cheap, light duty cutter and add a slipclutch, you have a cheap light duty cutter with a slipclutch. Use a Grade 8 bolt to attach the clutch to the gearbox and hope you can get along with it.
    We have too much gun control.
    What we need is more idiot control.

  7. #7
    Elite Member GManBart's Avatar
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    Belleville, MI
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    Massey Ferguson 241, Massey Ferguson 2244 crawler

    Default Re: PTO drive shaft sheering pins

    Quote Originally Posted by GManBart View Post
    If the slip clutch is set properly, I'd put a grade 5 or 7 bolt in it.
    Should have been grade 8....what I get for typing and talking at the same time!

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