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Stephen, can Rev Shackles...

Discussion in 'OffRoad Design' started by Shorts, Oct 16, 2001.

  1. Shorts

    Shorts 1/2 ton status

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    ..be used as a spring hanger in an SFA conversion on a '94 K1500? Or would there be too much pinion angle and wierd steering geometry and such?

    I got to thinking, if a stock rear spring hanger can be used as the rear hanger on the front set of springs, then would the reverse shackle be able to do the same job???

    What do you think?

    btw..I'm Shorts from the Off-Road BBS....AJM put me up to postin' this...I think he was too embarassed to ask....not to mention the fact that it was my question [​IMG]
     
  2. shaggyk5

    shaggyk5 1/2 ton status

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    Just a guess here, but i think that that might mess too much with the pinion angle/ steering junk like you suggested.

    --matt
    <font color=blue>86, 350 crate, 33's.</font color=blue>
    <font color=red>Lop Sop Doi Off-Roader</font color=red>
     
  3. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Hi Shorts, long time no see. Obviously I'm not Stephen but, I'll take a stab.

    The rear spring hangers are mounted outboard of the frame and the back side of the normal SFA front springs will mount directly under the frame. That could make things a bit complicated trying to mount the front inline with the rear (it would also need to be outboard) and the axle perch would likely (if the frame is similar to an SFA frame in width) need to be on top of the knuckle. [​IMG] Steering arm interference might also be an issue depending on how it is setup.

    As far as the pinion angle and steering geometry goes, I think that would be the least of your worries. Unless I am missing something, simply cutting the perches (necessary anyway if it is to line up with the relocated springs) and rotating as necessary would take care of that.

    Bad Dog

    85 K30 CUCV, 350 TBI, TH400, 205, D60/C14, 4.56 Locked
    Some day: 4" lift, 44" tires, massive cutting, shorter wb and rear overhang.
     
  4. Shorts

    Shorts 1/2 ton status

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    howdy baddog...glad to hear from ya! [​IMG]

    yeah, after reading and studying and looking and actually thinkin' - i came to the realization that the shackles as a rear mount would move the spring over too far and not allow for straight/parallel setup with the front spring mount.

    ok, back to the drawing board. i'm contemplating a setup using donor truck rear stock spring hangers to fit as the rear mount for the front springs.

    ok, all this rear/rear, front/rear spring thing has got me all finger-tied here [​IMG]

    <font color=blue>Shorts</font color=blue>

    '94 K1500
     
  5. j20m715

    j20m715 1/2 ton status

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    In reply to BadDog's comment on cutting &amp; turning to get pinion angle it will throw off camber &amp; caster on a frt axle. Just somthing to keep in mind.
     
  6. j20m715

    j20m715 1/2 ton status

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    Why not just buy the kit &amp; be done with it ?
     
  7. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    I was talking about just correcting for the change in spring angle, not changing the drivetrain geometry. As long as the drivetrain geometry does not change (not changing from u-joint to a CV shaft) then simply moving the perches to put the pinion back at the right angle will also keep the steering at the right angle. If you change the drivetrain geometry then you would need to rotate the diff or knuckles to keep steering working correctly.

    Bad Dog

    85 K30 CUCV, 350 TBI, TH400, 205, D60/C14, 4.56 Locked
    Some day: 4" lift, 44" tires, massive cutting, shorter wb and rear overhang.
     
  8. Shorts

    Shorts 1/2 ton status

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    the SFA kit from ORU? well, its $750...for brackets. By doing some homework, then paying the cost of materials, if that, then I can get my brackets for much, much less. Although it may be for some, I just don't have $750 lying in the couch cushions. and yes, i understand that at $750, I'm paying for R&amp;D as well [​IMG]

    As for ORD's 4" reverse shackle kit, I'm planning on buying those for the rear. $160 [​IMG] I know there's a God, and I'm glad that he loves 'wheelin' [​IMG]

    <font color=blue>Shorts</font color=blue>

    '94 K1500
     
  9. Stephen

    Stephen 1/2 ton status Moderator Vendor

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    I've seen axle swaps that used a stock tension shackle bracket at the back of the front springs, so if the stock brackets work, a flip kit should work in the same place, just with a lower mount point for the end of the spring. I saw this on Ned Bacon's solid swapper in Fourwheeler a few years ago. i think the stock hanger was from a 69-72 K5 and it used a 52" GM rear spring.
    If the front mount isn't built down some, you could run into some spring angle problems in the front. It's a pain to build around a spring that is radically different height from end to end. And it will probably introduce some weird handling, but I can't think of it clearly enough to write anything about it right now.

    Making the world better, one truck at a time.
    SW-ORD
    <a target="_blank" href=http://www.offroaddesign.com>www.offroaddesign.com</a>
     
  10. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Hmm, made me curious so I grabbed the flashlight and went out to have a look at my K30 (most of the front is off so easy access [​IMG]). Looks to me like if you used 1 ton hangers (close to the frame) the spring might barely clear the knuckle. However, this would cover the shock brackets (fab'd plates required I guess), interfere with the steering arm (x-over would fix), limit wheel turn (ouch) and place the steering box right over the spring (crunch). Hmm, late models have the box inside the frame don't they? Maybe not an issue for an SFA conversion.

    Never thought about leaving the front mount alone and angling the springs. Doesn't seem like a good idea but I can't think of a specific problem right now (other than the potential for binding that you mentioned). This is a bit intriguing as it would make adoption of longer front springs much easier. Unless I'm missing something (not the first time) it looks like too much trouble though.


    Bad Dog

    85 K30 CUCV, 350 TBI, TH400, 205, D60/C14, 4.56 Locked
    Some day: 4" lift, 44" tires, massive cutting, shorter wb and rear overhang.
     
  11. Blazr77400

    Blazr77400 1/2 ton status

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    I've got the March 97 Four Wheeler right here. He used a 72 rear spring hanger. He said you could also use a rear hanger off a 73-87 4x2. He says the 4x4 hanger wont work. He used the 72's because they swing 180 degrees. He needed it for the long travel suspension. The front mount is made from some homemade :odge spring hangers. The front springs are the rear 52" 8" arch, which had a 320 lb/in rating. Most other ones are in the 450 to 500 lb/in range. He removed the overload and also the shortest bottom leaf. For the rear he used a set of Skyjacker 5 1/2" that are 63 inches long. He added the shortest leaf that he removed from the front springs and then added a 3" block. That leveled the truck out. He can ramp a 1000 on the 20 degree ramp and it rides better then the old IFS.

    4 wheeling is like sex, when its good, its really, really good, when its bad its still pretty good.
     
  12. Shorts

    Shorts 1/2 ton status

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    late models have the steering box inside the frame.

    finding stock spring hangers shouldn't be too much of a problem...so i think i'll hit the junk yard and browse [​IMG] besides, i may go snag a CV joint off a wrecked truck to buy some time without spending an arm and leg. oh yeah, and too look for an axle....without that, brackets are useless [​IMG]

    k, question - what's the greatest angle that i can put on the axle....the angle that i'm referring to is the flat line from eye to eye against the spring pad on the axle. (i guess how perpendicular must those two surfaces be?) did that make any sense? hmm, now that i think about it, i guess i'd be measuring pinion angle....?

    <font color=blue>Shorts</font color=blue>

    '94 K1500
     
  13. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    All that work and he only ramps 1000 on a 20 degree ramp?

    Rene

    <font color=green>Dyslexics of the world...UNTIE!</font color=green>
    <a target="_blank" href=http://coloradok5.com/gallery/project_T2> tRusty pics...</a>
     
  14. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Well, as far as angles, you would need to keep the axle very close to its original orientation. Otherwise steering and pinion will cause you troubles. However, since the springs are not going to be in the same place anyway, this should not be a problem. You will need to move the spring perches on the tubes outboard (pretty much all the way to the knuckle) to fit the new springs so you just make sure that the axle is set right when you weld them back in the new location. The only problem with them being out of stock position vertically (with respect to each other) from front to back is a potential impact on steering behavior (as Stephen mentioned) due to different arcs when the spring is compressed or drooped. The "flip" idea might well exaggerate the problem. Maybe the front could be spaced down to make it closer. Several people have apparently built complete lifts like this. A sort of sub-frame in the front to move the spring mounts down and longer shackles (or sub-frame) in the rear to match the front offset. I'm not making any statements in support of the safety of viability of such a setup but it does provide lift without additional spring arch. If the springs are not parallel, then there is the potential for binding.

    BTW, out of that list from my earlier post, the only thing that would seem to be insurmountable for an SFA conversion is the tire hitting the spring at full lock. You'll need to check that clearance very carefully before committing. Also, I think (again, I may be missing something) that the springs being further out on the axle will have a slight negative affect on articulation due to reduced leverage.


    Bad Dog

    85 K30 CUCV, 350 TBI, TH400, 205, D60/C14, 4.56 Locked
    Some day: 4" lift, 44" tires, massive cutting, shorter wb and rear overhang.
     
  15. Blazr77400

    Blazr77400 1/2 ton status

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    He's got 20 inches of wheel travel front and rear. But I guess that isnt that much is it. [​IMG]

    4 wheeling is like sex, when its good, its really, really good, when its bad its still pretty good.
     
  16. Stephen

    Stephen 1/2 ton status Moderator Vendor

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    The IFS truck configuration is totally different than a straight axle truck. You use the same spring perches on the axle but the spring ends up mounted INSIDE the frame rail at the rear.
    i'm skeptical about the 2wd 73-87 hangers working, the offset from the frame is different than a 69-72.
    You should try to mount the springs pretty level in the chassis. A good starting point would be the stock GM mounting heights on the 73-up. that way your castor and pinion angles will at least be in the ball park.
    I would guess that Bacon's truck would do over 1K on a 20 degree ramp, it looks like it has more room to run. I know a guy in Denver that built an identical setup and it is pretty flexy. And besides, once you hit 1K on a 20 degree and have the ride quality you want, you're good enough for 99% of anything we can find to drive on. A lot of vehicles have limit straps and bumpstops to limit suspensions that were previously too flexy to work well.

    Making the world better, one truck at a time.
    SW-ORD
    <a target="_blank" href=http://www.offroaddesign.com>www.offroaddesign.com</a>
     

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