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Are there a lot of problems when running a 6 inch lift?

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by 72Blazerod, Apr 3, 2001.

  1. 72Blazerod

    72Blazerod 1/2 ton status

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    My buddy (79Jimmy) was considering 4 inch versus 6 inch lift for about a year. He decide to go with the 4 inch because he thought there would be too many problems with the driveline angle, u-joint and steering geometry. He is an engineer so I took his word for it.

    I would like to hear from those of you who do have a 6 inch lift. How does it ride? Is there an excessive amount of bumpsteer? Do you have drive line problems? Have you come up with any solutions to any 6 inch lift problems.

    I always thought bigger was better and I would love to put on a 6 inch lift with 35x 14x10's on my 72 Blazer. Am I in store for all kinds of nasty repair bills?

    Thanks again,

    Rod

    http://72blazerod.coloradok5.com
     
  2. Steve_Chin

    Steve_Chin 1/2 ton status

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    First off, I don't have any lift on my Blazer...

    As an engineer, I'd agree with your friend in that having less angle on the universal joints will reduce stresses on the U-joints and likely make them last longer. Also, adding lift tothe front of the truck will increase the lever arm length of the spring, increasing the amount of longitudinal displacement of the front axle during compression or extension, which will increase the amount of bump steer you will experience. My hunting buddy found that an S-shaped drag link helped to reduce the amount of bump steer he had in his 4" lifted Blazer after he ran a raised steering arm for a while (bump steer was BAD with the raised arm). He still has bump steer however, and the S-shaped arm brings a whole new problem into the arena in comrpession and extension deflection.

    Anyhow, that said, I don't think that the additional stress on the driveline will be a huge issue in 4" vs. 6" of lift. After all, look at how short the driveshafts are on the CJs and the lift they put on them (much more severe driveshaft angles, even stock!). The real problem to me would be bump steer. I haven't devised a good solution to this point and will likely just have to put up with it when I put a lift on my truck. The best compromise I've seen so far is the S-shaped drag link. I think that perhaps on a 6" lift using the raised steering arm with the S-shaped drag link might actually help a bit more than a stock arm with the S-shaped drag link on a 4" lift (just guessing now, since I haven't crunched the numbers).
     
  3. CaptCrunch

    CaptCrunch 1/2 ton status

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    the one thing I have learned is that when you lift a truck ity is all about comprimise... you can't have a perfectly smooth ride w/ no bump steer w/ a truck lifted 6".... heck even stock isn't that good. I plan on running a CV shaft and save all the hassles with driveline vibes... Steering will be interesting, but am going to try the 4" steering arm... if not add 2" drop drag link. I think some guys make a bit too much out of bump steer... don't want it then either spend big buck on a crossover steering or get an IFS truck.

    [​IMG]
    1987 Chevy K5 Blazer- 350 TBI
     
  4. Rasberry

    Rasberry 1/2 ton status

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    I have a 6 inch skyjacker lift on my 71 Blazer. The lift came with shims to correct the angle of the pinion. I had to have new custom drive shafts made because the original ones are to short. Also to help with the drive shaft angle in the back I had a CV-joint replace the standered u-joint out of the T-case. The front one already had a CV-joint. My truck drives great. Its no BMW but it rides like a truck should. No signs of wear on the u-joint yet. I would recomend the 6 inch lift from skyjacker. You can see how I lifted my truck on my web site.

    http://www.geocities.com/71blazer
     
  5. Quetzal_SJ

    Quetzal_SJ 1/2 ton status

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    beginer here!

    What is bump stering?

    Thanks
     
  6. Rasberry

    Rasberry 1/2 ton status

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    When you hit a bump the suspension moves up, which shortens the distance between the steering arm and the steering box arm. Your drag linkage isn't going to get shorter so it pushes the steering box arm, which well turn your steering wheel. Or the opposite could happen if you have a tight grip on your steering wheel the drag linkage will push on the steering arm on the axle and cause your wheel to turn.

    Hope this helps.


    http://www.geocities.com/71blazer [/url]
     
  7. harry

    harry 1/2 ton status

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    how come nobody is talking about cross over steering to correct the majority of the bump steer.

    harry
    69k5
     
  8. Rasberry

    Rasberry 1/2 ton status

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    I would be interested in hearing from someone that has done a cross over steering. What all is involved and how much mula did it take? If you've done this please share.

    Rasberry 71' K/5 Blazer
    http://www.geocities.com/71blazer
     
  9. CaptCrunch

    CaptCrunch 1/2 ton status

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    crossover steering is mucho denerio... gotta fabricate a lot of stuff or pay throw the nose. Is a great mod... a guy I know has it on his 8" lift blazer... turns like stock or even better.

    [​IMG]
    1987 Chevy K5 Blazer- 350 TBI
     
  10. 71RestoRod

    71RestoRod 1/2 ton status

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    Steve,

    Correct me if I’m wrong, but a dropped or s-shaped drag link can’t affect the bump steer at all, unless there is some dampening or spring effect happening from the s-shape itself. Granted, the tie rod ends are less prone to wear but even with the s-shape the steering geometry remains unchanged. A raised steering arm, however, will change the geometry.

    As for the crossover, here is my experience. I put a crossover setup in my ’49 Willys Wagon. Crossover provides a longer radius for drag link movement, but it can still be prone to bump steer if the angle of the drag link is too great. In the case of the Willys, I had good geometry, but (partially because of a go-kart like steering ratio) I found that I was getting feedback from the front springs swaying side to side. To solve that problem I had to install a panhard rod to hold the axle true. This had the added benefit of mirroring the horizontal movement of the drag link in the axle… and the bump steer went completely away. Personally, I wouldn’t attempt a crossover without the panhard.

    FWIW, I think that historically old cars and trucks were engineered with drag links along side the frame to minimize the squirrelly effects of the axles swaying side-to-side on the then very narrow and flexible springs.
     
  11. Steve_Chin

    Steve_Chin 1/2 ton status

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    The radius of travel of an S-shaped drag link is a bunch longer than a straight one would be with a raised steering arm. That's the reason that my buddy got less bump steer with the S-shaped link than with the raised arm.

    Crossover steering would be neat, but I'm gonna put a front bar on my Blazer, with which the crossover steering will interfere.
     
  12. Chris_T

    Chris_T 1/2 ton status

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    In a way you're both right. The S-shaped drag link does dampen the bump-steer a bit, but not a whole lot, it acts much better than a straight bar at an angle for steering, but not as much as crossover. I'd never actually considered the negative effects of the raised steering arm before Steve, that's interesting. I have a 6" lift with a 4" arm and a slightly angled drag link that needs replacing. My only option seems to be a 2" dropped link. No one makes them larger because of the angles involved, your friend's bar .. was it a 2" drop, or something cutom built? In theory a longer arm that still tracks horizontally sounds better, apart from the stresses of angling it a whole bunch. I'll probably put in the 2" dropped link just to bring everything back to the horizontal, maybe crossover if I ever swing a Dana 60 under there and don't have to start replacing knuckles and getting the maching done. The less extra steering inputs the better I figure, especially at 60 mph.

    CT
     
  13. Steve_Chin

    Steve_Chin 1/2 ton status

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    Chris, my friend's drag link is a 4" link, I think. The rod ends are close to horizontal.

    FWIW, I disagree slightly with a horizontal link being the best in all cases (given the stock steering arrangement - i.e. no crossover steering). The best link would be one that as closely as possible approximates the swing arm length of the front portion of the front spring (between the spring eye center and the axle center) and is also as close as possible to parallel with the line drawn between the center of the front spring eye and center of the axle tube. This will help t even out geometric changes between the suspension members through the travel of the suspension. Stock trucks were designed with a horizontal drag link because that was as close an approximation as the engineers could make. We got a lot of bump steer on a lot of different sports cars when their tie rods were horizontal...
     

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