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I may just 4-link the rear axle....

Discussion in 'The Garage' started by Greg72, Mar 30, 2007.

  1. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Hopefully in the next 30 days or so, I'll be receiving the new motor for the '72K5.... (502BBC)

    Not long after that, I expect to be having lots of leafspring problems due to axlewrap, so at the very least I'd need to add some sort of traction bar setup. I'd been wanting to add a softer set of leafsprings to more closely match what I have up front to get a bit more flex out back, but that would just make the axlewrap problems worse.

    As I was thinking it over, I realized that I already own a complete set of expensive, rebuildable heims. So for the price of some tubing (which I'd need to buy anyway to build the traction bars) and an inexpensive set of coil springs, I could actually just 4-link the rear and be done with it. I also have a set of Bilstein 7100 reservoir shocks that never got installed, so that might be a nice upgrade to add at the same time.

    The whole thing could probably be done fairly cheap...... the only thing I need to figure out is where to go for a ~250Lb/in coil spring that would give me about 5" of lift and maybe 14" of total travel????

    Any ideas? The rear of the truck weighs about 2500Lbs, and I can fabricate the mounts any way I want to accomodate the spring. I just need something with enough overall height to allow for the flex without binding.


    :thinking:
     
  2. y5mgisi

    y5mgisi 1 ton status

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    Forgive me for the blastphame, but there is a sight that is like ck5, but its for bronco's but i seem to remember them having some really good coil spring references(i.e. compresed heights, weight ratings, etc.) I dont remember the name but its one of the more popular ones.
     
  3. resurrected_jimmy

    resurrected_jimmy 1/2 ton status

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    Peterson's 4Wheel & off road.... "building a pre-mudder" they 4-linked a K5. I believe they used eibach springs
     
  4. ntsqd

    ntsqd 1/2 ton status

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    Different springs rates are easy, use coil-over springs even if not on a c/o. Take your best guess as to spring rate, order & try those. If you're off and you haven't scared the finish most vendor will exchange those you have for a different spring rate.

    The 14" travel part is the tough one. To get that you're likely looking at some OE application spring, which tosses the changeable rates thing out with the bathwater.

    If you go for a mid span mounting of the coils to one set of the links your spring rate will need to go up by the leverage ratio, but the spring's total travel will go down by that ratio.

    Easiest is to bite the bullet & go with coil-overs. Still can't get a 14" travel spring, but you can go to dual springs which will travel that far & farther. As a bonus or a hinderence depending on how you view it, with dual coils you can have a slinky-soft first coil sitting on top of a road going capable second coil.
     
  5. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    I'd forgotten about that 4WOR article....I'll go read that again.

    Mid-mounted springs sound like it may create some issues too. I need to think that one through some more.
     
  6. ntsqd

    ntsqd 1/2 ton status

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    Puts a bending moment on what ever arm you place them on, so those can't be a simple tube. Also means that the spring will try to 'roll' the link over if both pivots are SRE/JJ's/etc.

    There are two ways to deal with this. If coil-overs, put the lower mount of the c/o below the straight line thru the pivots. That will keep the arm alinged.
    The other method will work for just springs or with c/o's both. That is to make the front pivot not an SRE/JJ/etc. but more like a spring eye bushing only made from Delrin or similar. That will keep the link from 'rolling over.'
     
  7. garlicbreath

    garlicbreath 1/2 ton status

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    There was an article in one of the rags a few years ago about a first gen truck that the guy used the uber long 2wd rear arms to run coils. Used them all the way around. I wouldn't do it in the front, but it worked pretty well in the rear and cancels out the axle wrap.
     
  8. surpip

    surpip 1 ton status

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    hey greg put in a call to poly performance, they are a vendor on pirate, and from what i have read they are the go to guys for any thing coils.
     

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