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Flywheel Bolt Tension

Discussion in 'Early CJ5 and CJ6 Tech' started by RedWing, Sep 10, 2021.

  1. Sep 10, 2021
    RedWing

    RedWing Member

    Sutton Bay
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    Read through all the post and decided to order some ARP Flywheel bolts.

    then Jeep Manual says to torque to 50 to 65 pounds. The instructions that came with the bolts say 75 pounds.

    which should I follow?
     
  2. Sep 10, 2021
    jeepstar

    jeepstar Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Sheboygan
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    The manufacturer's specifications.
     
  3. Sep 10, 2021
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    What is special about the ARP bolts as compared to the flywheel bolts that came originally?
     
  4. Sep 10, 2021
    SFaulken

    SFaulken Active Member

    Bellevue, WA
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    When using ARP fasteners, always follow ARP's recommendation, as they aren't made from the same material, or have the same exact physical properties as the OEM ones. The steel is literally a different alloy. And I don't know about the flywheel bolts, but most ARP internal engine fasteners, like Head Bolts/Studs, Rod cap Bolts/Studs, and Main Bearing Cap Bolts/Studs, include their lube, and their published torque values are because you lube the threads.
     
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  5. Sep 10, 2021
    ITLKSEZ

    ITLKSEZ Hope for the best, prepare for the worst

    Liberty Lake, WA
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    One of the reasons a bolt “holds” is because at its recommended torque spec, it stretches a tiny bit and acts as a spring with preload. Not enough torque, and it doesn’t stretch. Too much torque, and it goes past its happy place and fatigues or all-out fails. If you’d only apply the stock torque to the ARP bolts, they wouldn’t have enough preload.
     
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  6. Sep 10, 2021
    Fireball

    Fireball Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Pullman, WA
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    This is correct, the proper torque generally depends on the bolt not the application. Ideally they are torqued to a stretch value but that's difficult to measure so a torque value is substituted. Lubricating the bolts before torquing gives more consistent results and ARP has their own lube used to create their own torque charts.

    ARP has a good explainer of proper bolt pre-load here: The Official ARP Web Site | Technical Information

    This is their torque chart (using their lube): https://arpinstructions.com/generaltorque.html
     
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  7. Sep 10, 2021
    RedWing

    RedWing Member

    Sutton Bay
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    Great advice! I’ll use ARP specs on both the fly wheel and clutch. Makes sense, thank you so much!
     
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  8. Sep 10, 2021
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    Is the lubricant essentially a type of antiseize?
     
  9. Sep 10, 2021
    SFaulken

    SFaulken Active Member

    Bellevue, WA
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    Honestly? I don't know what it is, exactly, but the closest thing I can compare it to, is a really light semi-fluid molybdenum grease. Or maybe oil impregnated graphite?
     
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  10. Sep 10, 2021
    Fireball

    Fireball Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    Agreed it's like a thin oily grease.
     
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  11. Sep 10, 2021
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    I've never used ARP bolts, so this is an interesting topic. Of course this goes against the general logic when it comes to the use of normal fasteners. :)
     
  12. Sep 10, 2021
    duffer

    duffer Rodent Power

    Bozeman, MT
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    Most ARP bolts are 8720. Pretty tough stuff.
     
  13. Sep 10, 2021
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

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  14. Sep 10, 2021
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    Reasonable over torque of course. :D
     
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  15. Sep 10, 2021
    Fireball

    Fireball Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Pullman, WA
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