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can extended front shackles affect caster THAT MUCH???

Discussion in 'The Garage' started by Can Can, Nov 12, 2006.

  1. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Would swapping out the stock 4" front spring shackles in exchange for 6" greasable ORD shackles alter the caster enough to bring on driveability issues on a 1989 V3500? If so, what's the fix?
     
  2. 79k20350

    79k20350 3/4 ton status

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    The fix would be to install shims to point the pinion back up. Why not just run the ones that are like 4.5" (which happen to be the same length as the ones you currently have) and are greasable? Going longer is also going to make your nonexistent shackle angle worse and make the truck ride crappier...
     
  3. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    This question is hypothetical, brother. I have to make some measurements before I continue with this line of thinking, but I wanted to learn some stuff in the meantime.
     
  4. 79k20350

    79k20350 3/4 ton status

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    Just trying to give you some all around info... As for driveablity isuse i couldnt tell ya as i dont have anything to go by, wish i could help ya more though:D

    Just wondering though, why go that much longer?
     
  5. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    My thoughts exactly...... PM headed your way.
     
  6. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Well I just got to take my truck for a longer drive and had a DW issue for the first time in over three years. Steering felt much more vague than I can ever recall.

    The only thing that has changed is I went from front shackles that were 4.5" long (47" springs and front shackle mount in stock location) to 7.25" long shackles and the shackle hanger moved up/forward. This did move the spring eye about 2" below the frame and seems to have affected caster enough to cause a bit of DW in my case.

    I'll take some measurements tomorrow and make some shorter shackles.

    So, I would say it is possible if you have longer than stock front shackles it could contribute to DW issues.

    Rene
     
  7. justhorsinaround

    justhorsinaround 3/4 ton status

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    Your steering geometry would be all hosed and would put a wrong constant load on the ball joints and just a bad idea IMO.

    Course I'm considered in many circles to be an idiot so.........
     
  8. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    The shackle being 2" longer than stock will lift the truck 1". It will affect caster angle but it won't affect his "ball joints" because a 1 ton has king pins. :D
     
  9. justhorsinaround

    justhorsinaround 3/4 ton status

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    Shut up ya know it all!!!:haha:
     
  10. muddysub

    muddysub 1 ton suburban status Staff Member Moderator GMOTM Winner

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    i put HILL4WD shackles on my suburban and developed a death wobble out of it... and the steering felt funny too.
     
  11. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Had to bust someones balls tonight. With a post count like yours you certainly aren't a noob and i would've expected more from you. :rotfl:
     
  12. justhorsinaround

    justhorsinaround 3/4 ton status

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    Yea well.

    You're just a big meany and I flat didn't draw the line between 3500 and 60.

    So shoot me!

    Meany.
     
  13. divorced

    divorced 3/4 ton status

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    Yep, same here. It was a lot more difficult to hold in a straight line on the highway. It had no "centered" feel. I'm guessing shims could have helped me.

    As mentioned, he has a Dana 60. Isn't there something that needs done (to the spring plates?) to use shims because of the two bolts that thread into the axle housing?



    .
     
  14. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    You can get away with 4* but anything more will want to bind the bolts.
     
  15. beater_k20

    beater_k20 Banned

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    shims and angled spring plates. i'm thinking shims on both sides of the spring pack isnt a good idea for some reason or another. :dunno:
     
  16. mrk5

    mrk5 The Sticker Guy Moderator Vendor GMOTM Winner Author

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    I was looking at doing the shackle angle/move the frame hanger thing this weekend. Based on the measurements I took you would probably between 5 & 6" shackles. That's with my 2.5" lift front springs.

    I think the 7.25" shackles are for the 52" swap where the spring is longer and hence the need for longer shackles than you would with stock length springs.

    This is the best explanation I've found for figuring shackle length:
    Canmore, I think you'd need to move the frame hangar to accomplish what you are after.
     
  17. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Yeah, I probably forgot to note that I'm running 49" long Alcan's up front. Measuring from the center of the old shackle hanger hole down to the lower bolt on the new shackle I'm running the equivalent of 5.5" shackles.

    I'm now thinking I need to shim the front diff.

    The Alcan's have about 2-3" of loaded arch and the center pin is 1.5" forward of center. I'm thinking the more forward location along the arch of the spring has tipped my pinion down...

    At any rate it is pretty squirrelly right now. :crazy:

    I'll have to bust out my angle finder and see what the caster angle now is and go from there. IIRC stock is supposed to be 8 degrees?

    Rene
     
  18. MarcS

    MarcS 1/2 ton status

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    Shims on a front axle scares me. I know it's illegal in NJ. Measure the castor, do the mods and relocate the spring perches back to the original castor angle. Do it right the first time.


    "Originally Posted by justhorsinaround
    Your steering geometry would be all hosed and would put a wrong constant load on the ball joints and just a bad idea IMO.

    Course I'm considered in many circles to be an idiot so........."


    Ball joints/kingpins, whatever. The centerline thru them is supposed to be at a certain angle so the steering is balanced (Not heavy or light feel). It should be to the manufactures specs.
     
  19. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    It's not like you can just 'move the perches' on a d60. You could move the drivers side, but the passenger side the perch is part of the center section.

    Doing a search I found this gem by Greg72

    He is running Alcan's and a D60 front as well.

    Rene
     
  20. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Well, I am at 11 degrees positive caster right now...

    As for what the caster should be I've seen everything from 4 degrees all the way up to 8 degrees mentioned as being the correct spec. Judging by the way my truck handles right now I'd say too much caster is just as bad as not enough. :crazy:

    I think tomorrow I'll pick up some 4 degree steel shims and see how much difference it makes.

    Rene
     

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