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Bucking Blazer -- 52" front swap Q

Discussion in 'The Garage' started by dremu, Dec 11, 2005.

  1. dremu

    dremu Officious Thread Derailer Premium Member

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    You know, like a bucking Bronco, except it's a Blazer.

    So I did the 52" front swap (along with crossover, highsteer, rear 56"s, and shock relocation on both ends. This stuff SNOWBALLS I tell you!)

    Test-driving the truck with the 52"s was SCARY ... above 20, 25MPH she'd start rocking on what felt like all four corners, like she was hitting some harmonic frequency, like those bridges you see shake in high winds... had to WHOA BABE her to a stop which made the Detroit start clicking on and off ... quite exciting :eek1: :crazy: Did that two or three times, that's enough for me.

    I put the original (4" Rancho, 47" or whatever) springs back on, no crazy bucking, even with the crossover and all the other stuff intact.

    The 52"s are of course softer than the Ranchos, but I would think I could get above 20MPH without shaking the truck apart. Is some component of the geometry THAT much different that the truck wants to vibrate apart? AZBlazer keeps going on about caster shims, but I didn't have any with the Ranchos and she drives solid with those.

    I used longer shackles in the back, of course, and lowered mounting points up front, all stuff I've seen other folks here do. The 52"s are a hair taller than the Ranchos with all that, but by less than an inch, I believe. I would guess, though I have no way of measuring, that the caster isn't changing much between the sets of springs.

    One thing I did notice is that my driver's side perch is hogged out, and it's possible that the spring on that side can't seat properly? (attached)

    Any other ideas gladly entertained, as I'm more than a bit pissed I spent several hundred bucks and a LOT of time to make my truck undriveable :haha::rolleyes:

    -- A

    springperch.jpg
     
  2. ryan22re

    ryan22re 1/2 ton status

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    when i swapped out my 10 bolt, i noticed that my perch was hogged out too. but mine was stock. it seems that the spring had to have been moving to waller the hole like that. perhaps the springs were moving around, causing what you are describing? i also wonder about the caster change from 52's to your ranchos. perhaps the 52's dont provide enough caster? did you have it aligned to see?


    ryan
     
  3. dremu

    dremu Officious Thread Derailer Premium Member

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    Your tag line is fantastic, btw. Great movie ... 'course, I like Milla. "CHICK-UN!" ... anyway.

    Nope, didn't check alignment ... I wouldn't have been able to get it to the shop unless I towed it. Any takers on whether less caster would make my truck hop like it was dancing?

    -- A
     
  4. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Sounds a lot like DW to me...was the steering wheel rocking violently side to side?

    Rene
     
  5. 89GMCSuburban

    89GMCSuburban 1/2 ton status

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    DW on a ball joint 10 bolt?

    Are all your shocks NEW?

    Mine did that on the drive up actually, even with new shocks. I had 33's on and the sway bar HAD to be on to stop it. Put the 36's on and it doesn't matter anymore. What size tires were you test driving with?
     
  6. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    DW on a 10 bolt or a 44 is possible...

    Rene
     
  7. readymix

    readymix 3/4 ton status

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    I had the DW in my 98 Z-71. The bushing around the sector shaft was wallowed out. I T/S that stupid thing for over a month before Tom Allen (from PSC) told me what to check.....
     
  8. dremu

    dremu Officious Thread Derailer Premium Member

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    10 bolt with D44 knuckles for XO, yes.

    Front shocks are brand new. 35" tires. Same as before. Note also that I switched ONLY the front springs and mounting and the problem went away, or at least was much less pronounced.

    I thought DW was a D60 thing to do with kingpin preload.

    I also swapped the knuckles into this axle for the XO, and put in new ball joints ... thought I did them right, per the factory book of torques.

    -- A
     
  9. dremu

    dremu Officious Thread Derailer Premium Member

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    Acha! How does one check it? Make sure the shaft rotates in line and doesn't wobble?

    (And what's "t/s"?)

    -- A
     
  10. dremu

    dremu Officious Thread Derailer Premium Member

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  11. sled_dog

    sled_dog 1 ton status

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    I've had it before where my toe was bad, I could literally feel one wheel and the other catching as the truck went back and forth trying to follow the pointed in wheels. it can be a nasty thing.
     
  12. dremu

    dremu Officious Thread Derailer Premium Member

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    And in the Pigpen we say that all toe is good :haha:

    Yeah, it was amazing ... I guess with the softer 52"s the tires could hop up whereas with the Ranchos they just scrubbed ... wow.

    -- A
     
  13. jays68yak

    jays68yak 1/2 ton status

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    So are you going to put the 52s back in?

    On a side note....I think my toe is off a bit and I had some DW atfirst but then added a spacer to each kingpin. Maybe I should adjust it before the next trip.
     
  14. dremu

    dremu Officious Thread Derailer Premium Member

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    Yup, put them back in this morning. I've got the springs-and-mount changes DOWN, I tell ya :haha:

    So what does changing the kingpin loading do? Tightens the knuckle to the C so it doesn't turn as easily?

    -- A
     
  15. jays68yak

    jays68yak 1/2 ton status

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    im using the WFO arms which use shims instead of the king pin spring. So to adjust the preload you add or remove shims.
     
  16. dremu

    dremu Officious Thread Derailer Premium Member

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    Okay ... but what's that do? Tighten the knuckles so they don't turn as easily? Change camber or something?

    -- A
     
  17. sandawgk5

    sandawgk5 3/4 ton status

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    It forces the bushing down on the Kingpin cone which does make the steering tighter but in actuallity you are centering the knuckle around the kingpin. DW is when the spring does not have enough pre-load on the bushing and allows it to ride up off of the kingpin and allows the knuckle to no longer be centered on the kingpin. It does not only occur on Dana 60s or kingpin axles. I had it occur on my 1981 Chevy Luv 2WD. The tie rod ends where worn and let the spindles oscilate back and forth with no steering input. If ball joints are worn the same thing can happen also.

    Ira
     

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