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Thread: Pin Box Loose

  1. #1
    thompsjk
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    Pin Box Loose

    I have a Momentum 385 and noticed that paint around the bolts on the pin box is worn off and it looks like the pin box is shifting. I then found that two of the bolts were not much more than hand tight. What is the torque spec. for these bolts. They are 5/8" Grade 5 bolts.

    Thanks
    Jeff

  2. #2
    Rolling Along
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    I installed a 5th Airborne pin box on our Reflection. The installation instructions specified 150 Lb/Ft for 5/8" Grade 5 bolts.
    Nick and Nancy
    Abbotsford BC
    2011 Ram 3500
    2015 Reflection 303RLs

  3. #3
    Seasoned Camper
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    We have a 385, (2015) and it the black bag that has all the manuals, we got a master manual for Lippert components. On last page, (107) has general maintenance section which calls out pin box It states110 ft/lbs for torque on mounting bolts. And it also tells you about grease points and so forth. Hope this might help some, Hootie

  4. #4
    thompsjk
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    According to my engineering hand book 5/8" grade 5 coarse thread bolts has a max torque of 154 foot pounds. It also states that grade 5 as the min for metal to metal structural steel with grade 6 or higher recommended.

  5. #5
    Site Sponsor Cate&Rob's Avatar
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    Quote Originally Posted by thompsjk View Post
    According to my engineering hand book.

    First thing that occurred to me when I read the question . . . but, mine is in a box somewhere !

    Rob
    Cate & Rob
    (with Border Collies Molly & Angel and their kitty Gracie)
    2015 Reflection 303RLS #792
    2014 F150 EcoBoost 4x4 Crewcab with Max Tow and Heavy Payload pkgs
    Whitby, Ontario, Canada

  6. #6
    Seasoned Camper
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    LCI stated 110 in the book. We only use grade 8 bolts at work and use the torque spec the different manufactures give us.( depends on what I am working on) you would think same size bolt would be same torque specs. But every manufacture has there on engineering and they have their on torque specs. I work in the oil/gas industry and work on high pressure equipment and we live by torque specs. do not want to stretch the threads where they will not hold and back out. I did read where You said max torque of 154. Did the book give a +/- ft/lb with the max 154 ft/lbs. I think I would give LCI a call and see for sure what they torque them to,.you never know what their engineering will say. you got me thinking I might have to call now. Hootie

  7. #7
    Site Sponsor Cate&Rob's Avatar
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    The max torque that the bolt threads can withstand is not necessarily the compression that the joint needs.
    Also, painted surfaces or plated bolts will eventually reduce the joint compression and relax the torque from what was originally set. This would cause a manufacturer to spec a higher torque for new parts than what used parts should be torqued to. Whatever you choose to torque these bolts to . . . it is really easy to re-check this. I would do this after the next few trips.

    Rob
    Cate & Rob
    (with Border Collies Molly & Angel and their kitty Gracie)
    2015 Reflection 303RLS #792
    2014 F150 EcoBoost 4x4 Crewcab with Max Tow and Heavy Payload pkgs
    Whitby, Ontario, Canada

  8. #8
    Seasoned Camper
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    I got a hold of LCI today and asked about torque values for the pin box on the Momentum385th (Roto Flex) and they gave me the torque spec they recommend. 95 ft/lbs to 110 ft/pound with bolts they are installing with. When I said do not want to stretch the threads above, I was talking about over torque. The reason for torque values and correct compression. Hootie

  9. #9
    thompsjk
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    Most after market replacement pin box manufacters recommend 135-150 foot pounds. When I have time I will probably change the bolts to a grade 8 and go to 150 foot pounds.

  10. #10
    King Pin
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    Quote Originally Posted by Cate&Rob View Post
    The max torque that the bolt threads can withstand is not necessarily the compression that the joint needs.
    Also, painted surfaces or plated bolts will eventually reduce the joint compression and relax the torque from what was originally set. This would cause a manufacturer to spec a higher torque for new parts than what used parts should be torqued to. Whatever you choose to torque these bolts to . . . it is really easy to re-check this. I would do this after the next few trips.


    Rob
    I retired from the missile manufacturing business last year, and proper torque was always a hot topic (pun intended). I'm sure you can imagine that the vibration during missile flight is severe, and proper torque is critical. A typical missile flight is a couple of minutes. However, our rigs are vibrating and flexing mile after mile, day after day. They also see pretty robust temperature fluctuations over time. We got to the point where we'd take a missile at ramdom once a quarter and completely tear it down. During the tear down process, we'd record the torque value on each fastener before we removed it. In most cases, a hard surface torque value would relax 15 to 25 percent! However, if a fastener had been torqued, then subjected to temperature and vibration and retorqued, it would retain it's torque value within five percent. The loose fasteners you found in your pin box sound like typical cases of a fastener losing its torque value over time and then starting to back out. So I'd suggest that once the proper torque value is determined, all owners should check important fasteners from time to time to make sure they have not relaxed. If you check them once after a few hundred miles and a few weeks, they will likely stay at the proper torque value.

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