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What to torque a 3/8" grade 8 bolt to??

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Eric M., Oct 18, 2002.

  1. Eric M.

    Eric M. 1/2 ton status

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    What to torque a 3/8\" grade 8 bolt to??

    The back rear spring perches on my truck were sheered off. I will be bolting them back on with grade 8 hardware. I can't find any torque specs in my shop manual since these were originally fastened with rivits. Is there a general rule of thumb for torque specs based on size and grade?

    Thanks,

    Eric M.
     
  2. heavy4x4

    heavy4x4 1/2 ton status

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    Re: What to torque a 3/8\" grade 8 bolt to??

    Do you mean the whole shackle where it connects to the frame sheared off??? /forums/images/graemlins/shocked.gif That takes some serious abuse to do that.
    As far as torque, a standard (grade 0-2) 3/8" bolt should be torqued to 30 ft. lbs. I wouldn't have a problem torqueing a grade 8 to around 60-75 ft lbs. Just put a lock washer on, torque the bolt to 60 ft lbs. and make sure the washer is smashed down. You should be fine.
     
  3. imiceman44

    imiceman44 1 ton status

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    Re: What to torque a 3/8\" grade 8 bolt to??

    with grade 8 of that size you could easily go to 90-100lbs
    You could also enlarge the holes and go with bigger bolts. /forums/images/graemlins/thumb.gif
     
  4. Blazer1970

    Blazer1970 1/2 ton status

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    Re: What to torque a 3/8\" grade 8 bolt to??

    Don't go above about 45 lb-ft with a 3/8 fastener. You want to preload it, not break it. Use hardened lock washers.
     
  5. sleeper_dave

    sleeper_dave Registered Member

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    Re: What to torque a 3/8\" grade 8 bolt to??

    When i replaced the spring perches on mine, i used a 1/2" ratchet and torqued it as hard as i could. It hasn't come loose or broken any bolts yet, and i've taken it through some stuff since then.
     
  6. imiceman44

    imiceman44 1 ton status

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    Re: What to torque a 3/8\" grade 8 bolt to??

    Now that would be a lot, I used to do that before I got the torque wrench, now I found that most times I got 200lbs, that's why I use the torque wrench now.
    Head bolts are torqued around 180lbs and they still work the same way loaded not to the point of stretching. 90 isn't too much, but you could go with 45 wih a lock nut, that will keep the pressure on and make sure the bolt doesn't loosen up.
    You might also want to invest in a little loctite.
     
  7. Shaggy

    Shaggy 3/4 ton status

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    Re: What to torque a 3/8\" grade 8 bolt to??

    <font color="green"> Here you go - Torque specs </font color>
     
  8. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Re: What to torque a 3/8\" grade 8 bolt to??

    Dude, what head bolts are you torquing that are 180 ft. lbs. /forums/images/graemlins/shocked.gif Small block chevy's are 65 ft. lbs.
     
  9. Eric M.

    Eric M. 1/2 ton status

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    Re: What to torque a 3/8\" grade 8 bolt to??

    Thanks Shaggy,

    That's what I was looking for.

    Eric
     

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