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Driveline Issues with 4" Skyjacker Lift

Discussion in '40- & 55-Series Tech' started by arizona78, Nov 18, 2003.

  1. arizona78

    arizona78

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    I have a stock '78 FJ40. I'd like to install the 4" Skyjacker lift kit, retaining the stock length shackles. Is a 4" lift enough to cause drive shaft issues (binding, too short, etc.)? How high of a spring lift is possible before you run into issues with the driveshafts? Is the 2 1/2" lift a better choice? I just don't want to spend the money to install the kit only to have to spend a bunch more money to correct any problems it causes...
     
  2. Archengine

    Archengine

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    I went with a 2.5 inch lift with my springs, shackle rev, and 1.5 inch lift shackles in the back. 4 inches of lift and finally a smooth ride. If you want a 4 inch lift go this route, as 4 inch lift springs alone will be harsh. My rear driveline is fine, but the front one needed a spacer that I had to buy. A good complete kit should include this spacer, which is really just an aluminum disk around an inch thick that lengthens your front driveshaft. If not, I believe I have one still after I lengthened my driveshaft in the front, if you need it. But you can also get them from Downey and other places.
     
  3. CruisinGA

    CruisinGA

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    I installed 4" Skyjacker. The ride is not harsh, but not silky smoother either, I prefer to avoid extended shackles. (1.5" extended adds only .75" of lift). The only thing that is required outside of what is included in the lift is a longer rear brake line, available in stainless steel from skyjacker. I went ahead and installed greasable anti-inversion shackles. Don't forget that you need 8 more stock size bushings, available in polyurethane from SOR and other vendors.
    I did nothing to my drivetrain, I have fully flexed the suspension to its limits with no side effects. While my driveshaft lengths are probably not optimal, I knew I would be installing a new transmission soon that would alter driveshaft lengths anyway.
    Be aware that if you have any marginal u-joints, especially in the rear shaft that may not be noticeable right now, a lift will likely cause them to fail and become noticeable. This happened to me, I replaced the failed u-joint, not another problem, 6 months later.
    You may or may not need caster correction shims with lift springs, with 2.5 inch lift springs probably not. I wouldn't need caster correction shims if my cruiser was not a DD that also got flat towed. The flat towing really brought out the lack of caster (bad tracking). I am installing 2.5 degree caster shims from this weekend to hopefully remedy that situation.
    Only "problems" that the lift itself has created-
    1)finishing off an already gone u-joint
    2)longer rear brake line
    3)caster correction shims.
    Thats it for me. Good times, and go for the SJ 4", you won't be disappointed.
     
  4. FJ60

    FJ60

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    my 4" TPI lift came with everything including 6 degree shims for caster correction on the front (fat end forward :D) I replaced the u-joints while it was apart and have had zero problems.
     
  5. willsta2000

    willsta2000

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    I personall ran a Skyjacker 4" the last year+ with no driveline issues to speak of. On top of that, I installed MAF's shackle reversal kit which lifted me another 1.5",... granted my front driveline was just a scoche too short, but I never had it pull apart on me in 10 mos,... came close though. However, when I put my 3" extended shackles on the rear (to compensate for the additional height up front), the shackles caused me some rear driveline turmoil, but nothing 6 degree shims couldn't solve.

    Basically run lift springs or shackles, but not both. IMO

    WILL
     
  6. fjcruiser

    fjcruiser

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    I think it depends on how large of a tire you want to run. I think if you want to run 33's you should probably go with the 4" kit.
    I have a 4" skyjacker lift, 2" ext. shackles, cut fenders and run 35" mtr's no problem. I'm not sure I could run the 35's without cutting the fenders.
     
  7. 1Fine40

    1Fine40 Rust Buster SILVER Star

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    I've got the 4" SJ kit, and here were my issues: 1st, the springs are nice and flexy after break in, but they would tend to have the spring eye smack the frame at the rear corners when you hit a big bump like say a water channel at intersections at medium speeds. Solved that by adding longer (1.5") shackles at the rear. Bigger arc for the springs to travel now, and they don't bottom against the frame, but now for issue #2. After the extended shackles, I got rear DL vibration....Solved by adding correct shim to pack to re-orient DL flanges parallel with each other. (I think it is a 2 degree..?) Since then, the kit works well, and yes, I did replace the rear brake line from the frame to the tee with a longer one. YMMV. :cheers:
     
  8. purefj40

    purefj40

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    It's odd to me that the spring manufacturers don't include that info. Hundreds of people are getting SJ 4" lifts, yet it seems like everyone has to guess or do a ton of research to get it right.

    So it seems that with a 4" lift and 33s, you need the following:
    extended brake lines
    caster correction shim of some size
    Extended shackles
    Driveline spacer
    New U-joint

    Does that about cover it?
     
  9. CruisinGA

    CruisinGA

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    The only part that we all agree that you will HAVE TO BUY is the brake line.
    The other parts are the result of some other part or condition.
    Caster Correction Shim-Normally not absolutely necessary up front with stock length shackles and SJ springs, unless you flat tow. Will improve handing when installed. Only necessary in the rear with extended shackles.
    Extended shackles-I'm running the tires listed in my sig line with no extended shackles without any problems. I could fit 35's without extended shackles if I so desired. (my rear fenders are cut)
    Driveline spacer is not always necessary. Myself and others have run skyjacker 4"er without these with no problems.
    A new u-joint would only be necessary if you have an already bad one fail after installing the lift. Thats just what happened to me and has happened to other people.
    Parts that YOU MUST BUY that are not included:
    1)The previously listed extended brake line
    2) 8 Stock size poly bushings for frame to shackle eyes. (SOR)

    Recommended:
    I would recommend having new stock length greasable shackles on hand, this way do you not need to worry about damaging your old ones, and are probably already worn. I like the SOR greasable anti-inversion ones.
     
  10. fjcruiser

    fjcruiser

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    Like Cruisin' said, all you "need" is the brake line and bushings. I don't think that you need the shims unless you do ext. shackles as well. You will "feel" the need for shims. I got 2 deg. and they took out most of the driveline vibration. I didn't need a drivline spacer. I think this would only be related to shackle reversal in the front.
     
  11. cavsfj40

    cavsfj40

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    My skyjacker kit included the bushings and i aqm rumming the stock line in the rear, it is tight and unsafe, but free for now.flexed the hell out of it and didn't pop the line and i have had no driveline issues either. I am running 1" over shakles in the front and 2" in the rear
     
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