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  1. #1
    Bronze Member
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    Default Kubota L4330 - Loader bolts missing / threads mashed / stripped threads

    Hello everyone,
    I have a L4330 with the larger loader and for some reason my unit has loosed the lower loader bolts as well as in some of the bolts mushed the threads to the point that the threads have stripped.

    I do have the additional brackets to support the ability to mount the sub frame when removing the loader to put in place a snow blower.

    The threads are fine pitch - first of all, does anyone know the size of these mounting bolts?
    Any idea why my bolts are loosening?

    For the threads that are stripped, I will have to drill out and re-tap to the next largest size.
    Thanks
    Scott

  2. #2
    Veteran Member rScotty's Avatar
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    Many in the past. Today, a Kubota M59, JD530, JD310SG, Ex-Yanmars - 16 & 33 hp - now gone but never forgotten

    Default Re: Kubota L4330 - Loader bolts missing / threads mashed / stripped threads

    Before drilling out, I would try to chase the threads that are there with a fresh tap. Go slow and clean the tap often. There is some debate among engineers as to how many complete threads are actually needed to hold full bolting torque. I've heard as few as 3 and as high as 6 threads. The point being that that you may be able to torque and use the damaged threads. Loctite has largely taken over from the old fashioned lock washers. Nothing beats safety wire.
    rScotty
    Pride of place goes to our 2 cylinder John Deer 530. With her QA loader, smooth draft control, telescoping 3 pt arms, pwr steering, clutched PTO, comfortable seat, and remote hydraulics she's as useful today as 50 years ago. There's a Kubota M59 & a JD310SG for TLB work....giving us options on doing heavy jobs.
    We'll not forget Mr. Big & Mrs. Little - 33 & 16 hp Yanmars - now gone, but never forgotten.
    And a line-up of well-used implements that still work better than they look.


  3. #3
    Super Star Member murphy1244's Avatar
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    Ohio
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    Kioti DK-40

    Default Re: Kubota L4330 - Loader bolts missing / threads mashed / stripped threads

    You need 1x dia. for thread engagement. Use blue Loctite.
    Murph ------------

  4. #4
    Super Member
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    Feb 2006
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    JD2010, Kubota3450,2550, Mahindra 7520 w FEL w Skid Steer QC w/Tilt Tatch, & BH, BX1500

    Default Re: Kubota L4330 - Loader bolts missing / threads mashed / stripped threads

    Quote Originally Posted by nvr-enuf View Post
    Hello everyone,
    I have a L4330 with the larger loader and for some reason my unit has loosed the lower loader bolts as well as in some of the bolts mushed the threads to the point that the threads have stripped.

    I do have the additional brackets to support the ability to mount the sub frame when removing the loader to put in place a snow blower.

    The threads are fine pitch - first of all, does anyone know the size of these mounting bolts?
    Any idea why my bolts are loosening?

    For the threads that are stripped, I will have to drill out and re-tap to the next largest size.
    Thanks
    Scott
    Yes. Something is wrong with the setup of the loader on the tractor. Sorry that it is impossible to be specific, but some possibilities are:

    #] It does not fit the tractor exactly and correct shimming or other measures were not taken to assure neutral compliance at all fastening points.
    #] The loader frame is missing some bolt in brace elements.
    #] Correct fasteners and hardware, washers, etc were not used
    #] Any or all fasteners were never tightened. These bolts are meant to be very tight. Check specs.

    ,,,The last is the most likely to be a sole cause, but combinations with any or all would ensure speedier failure.

    Who installed the loader?
    larry
    This side of 40
    JD2010, Kubota L3450/FEL w SK QC, L2550 w FEL
    Mahindra 7520 [Pinky] /FEL w Skid Steer QC/w Tilt Tatch & BH, BX1500 [Mighty Mouse]
    IH37 Baler, CCM165 Drum Mower, JD Rake
    JD 127 bushog, Flail, SK Tilt Tatch , KK tiller, Rhino rear blade, Post driver, post auger, chipper, pallet fork, Grapple/Loader Buddy, Homemade Splitter/DC Welder

  5. #5
    Super Member crazyal's Avatar
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    Northern Vermont

    Default Re: Kubota L4330 - Loader bolts missing / threads mashed / stripped threads

    You may need to repair the threads with a heli-coil.
    Kubota L4240,Case 580K backhoe, Case 450 Dozer

  6. #6
    Super Member
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    JD2010, Kubota3450,2550, Mahindra 7520 w FEL w Skid Steer QC w/Tilt Tatch, & BH, BX1500

    Default Re: Kubota L4330 - Loader bolts missing / threads mashed / stripped threads

    Quote Originally Posted by crazyal View Post
    You may need to repair the threads with a heli-coil.
    Heli coil repair is not suitable for threads in that type of service
    This side of 40
    JD2010, Kubota L3450/FEL w SK QC, L2550 w FEL
    Mahindra 7520 [Pinky] /FEL w Skid Steer QC/w Tilt Tatch & BH, BX1500 [Mighty Mouse]
    IH37 Baler, CCM165 Drum Mower, JD Rake
    JD 127 bushog, Flail, SK Tilt Tatch , KK tiller, Rhino rear blade, Post driver, post auger, chipper, pallet fork, Grapple/Loader Buddy, Homemade Splitter/DC Welder

  7. #7
    Super Member crazyal's Avatar
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    Northern Vermont

    Default Re: Kubota L4330 - Loader bolts missing / threads mashed / stripped threads

    They have been used by others here that have had the same problem with success. We use them at work all the time and I've never heard of a limitation. Do you have documentation? I would like to read up on it.
    Kubota L4240,Case 580K backhoe, Case 450 Dozer

  8. #8
    Super Member Coyote machine's Avatar
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    '10 Kioti DK 40se/hst KL-401 FEL, loaded tires, KB-2485 bhoe, Tuffline TB160 boxblade, Woods QA forks, MIE Hydraulic bhoe thumb & ripper tooth, Igland 4001 winch, & GR-20 Log Grapple. Woods BBX72" Mower. Diamondplate aluminum canopy.

    Default Re: Kubota L4330 - Loader bolts missing / threads mashed / stripped threads

    Do the existing bolts go all the way into the hole or are there threads not being used by the bolts further into the hole? I ask this because I had the same problem on my loader, and found that by lengthening the bolts with new ones that used the whole hole depth I was able to grab more threads, and thus tighten the new bolts tighter, with red locktite. Problem solved. Fortunately I got to it before the thread holes were totally mangled. I replaced all bolts on both sides. In this case it was use of too short bolts by the manufacturer, and I confirmed with my dealer that when they get too far gone they have to remove the loader and do a bolt and nut routine. Way too much work for such a simple problem- if only the right length bolts had been used to begin with....
    2010 DK-40se/hst, Kioti KL-401 FEL, (reversible Kioti cutting edge), 72" Ratchet Rake. Fit Rite Top-N-Tilt hydraulics & diverter valve. HLA Series 2000 7' snowplow, Aquiline MPC rear chains. Samuri Sickle bar.

    Scag Wildcat: Kawasaki 26HP, with bagger. Dr. brush mower, & 42" lawn deck, Dr. self propelled, 6.5HP Trimmer mower. Pro-Mow 3 gang mower, no HP.

    Bunch of STIHL chainsaws: 011x 2, MS192T, MS200T, MS180C, MS230, MS270 (Wood Boss), 038 Farmboss, '86 anniversary edition.

  9. #9
    Veteran Member rScotty's Avatar
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    Default Re: Kubota L4330 - Loader bolts missing / threads mashed / stripped threads

    Quote Originally Posted by murphy1244 View Post
    You need 1x dia. for thread engagement. Use blue Loctite.
    Murphy, that's a nice rule of thumb; I like it enough that I often use it myself. My thought is that rule came into popular use because it is a nice approximation of the thickness of the standard nut for each bolt....and how could that be wrong?

    But it isn't the last word.
    If you want to go into more detail, check out:
    trwww.engineersedge.com/calculators/iso-minimum-thread-engagement.htm
    There calculations come closer, but there's problems with that approach too.

    Scott, it's a nasty problem. There might be "helicoil type" inserts that would work; I don't have any experience with them. But they all require hand-tapping into the cast engine block material and that would be a problem all by itself. Last resort.

    I like the fix that Coyote came up with. Somehow you need to get a bolt out and measure the depth of unused thread in the block. There will be some.....hopefully there will be enough. Then decide what thread you have and go to McMaster Carr to get some.

    Now the choice is whether to use a new tap and carefully chase out the damaged thread. As to how to do the thread restoration.....
    I've actually had better luck restoring damaged threads by not using a commercial tap at all - commercial taps are too sharp with too much cut and not enough thread support. Too easy to get them started wrong and they will cut regardless of right or wrong.

    What I do is better and costs less. Take a hardened bolt of the right thread and size and cut half a dozen slots with a hacksaw perpendicular to the threads. Cut the slots about an inch long and somewhat deeper than the minor thread diameter. Now carefully taper the bolt for the first couple of threads. If you want, I can probably find an old bolt I've done this to and post a picture. This becomes my handmade thread restoration tap. It is way better for the purpose than a tap. Start it straight, go very slow with lots of light lube, and the real trick is to back it out to clean the particles with a hand wire brush quite often. Sometimes I back out every 1/8 turn I gain....or even more often. Constantly cleaning the particles out of the hand-made restoration tap is critical to doing this job. Each time you back the hand-made tap out, Use WD-40 and a nozzle to foam out the particles left behind in the thread bore.

    When done, try to thread in the longer bolts you bought - best source for those might be at McMaster. With luck, there will be enough good thread to hold the torque. That's not quite as good as new, but I can't think of a better solution. Be careful not to use too long of a bolt. You'll probably have to cut them to special length. Use hardened washers. Measure to leave a little free space at the end. You sure don't want to go too deep and crack the casting.

    What a pisser. Yes, the original bolts were more than likely poorly installed. This is as good as I can come up with. Don't give up on the threads you have until you've tried every way to get them into use again. Anyone else?
    luck, rScotty
    Pride of place goes to our 2 cylinder John Deer 530. With her QA loader, smooth draft control, telescoping 3 pt arms, pwr steering, clutched PTO, comfortable seat, and remote hydraulics she's as useful today as 50 years ago. There's a Kubota M59 & a JD310SG for TLB work....giving us options on doing heavy jobs.
    We'll not forget Mr. Big & Mrs. Little - 33 & 16 hp Yanmars - now gone, but never forgotten.
    And a line-up of well-used implements that still work better than they look.


  10. #10
    Veteran Member
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    Kubota L3800DT, L3750DT Shuttle

    Default Re: Kubota L4330 - Loader bolts missing / threads mashed / stripped threads

    It is a known fact that the loader frame bolts need to be checked routinely when the rig is new. I believe it is mentioned in the owner's manual.
    Don
    Kubota L3750 Hydro Shuttle, 4wd, FEL; L3800 Gear drive, 4wd, FEL
    Husqvarna XP chainsaws 346xp X3, 357xp, 562xp, 359

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