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Death Wobble

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  • Death Wobble

    So I was watching the latest Dirt Every Day ( my favorite on MT on demand ) and they put together this pacer with Dana 44s solid axles front and rear . This thing had death wobble so bad that they really couldn't drive it on the street . I've heard of this before ( I think Loren ) but never actually knew what it was till today . They had a camera on the front suspension. What causes it and how do you get rid of it ? On of these days I'd like to solid axle swap my 94 Suburban that currently has a 6 inch lift on the IFS and I would like to not have this problem .
    Previously HoosierL98GTA

  • #2
    I'd get a death wobble (at least that's what I'd call it) on my mountain bike when the back wheel was out of true and speed approached 60mph. Never in a car though.
    I'm probably wrong

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    • #3
      On a regular car too much Caster does that. Like a shopping cart going too fast.
      My hobby is needing a hobby.

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      • #4
        All of the Jeeps I've owned with trailing arm front axles (2 XJ's, 1 TJ) have developed death wobble at some point. The cheap easy fix is stab bar links, steering shock, and a track bar (my green XJ). The expensive time consuming fix is axle universals, ball joints, hubs, shocks, stab bar links/bushings, steering box, steering shock, tie rods, and track bar, tires (wife's TJ, yes it was that worn out under 100k). I've learned over the years that the primary cause of death wobble is usually stab bar links/bushings, steering shocks and track bars. My last go around with death wobble on the green XJ (I've owned it since 06) involved replacing the stab bar bushings and steering shock. The stab links and track bar were fine this time around, and the Jeep drove like a different vehicle with those parts installed.

        It's hard to isolate what's worn out on a trailing arm front axle being that there's so many components involved. My buddy Matt experimented with the death wobble cure by replacing nearly everything on the front end of his TJ. He replaced the trailing arms and bolts, axle u-joints, ball joints, hubs, shocks, stab bar links/bushings, steering box, steering shock, tie rods, track bar, tires. He eventually cured the death wobble, and most of the parts on the list needed to be replaced at some point, but he said all that really needed to be replaced to cure the death wobble was the stab links, steering shock and track bar. Things get more complicated when lifts and big tires are involved though. You end up having to run offset ball joints and fully adjustable track bars and trailing arms to keep the wobble at bay.

        Kevin's Off Road did a write up on death wobble a while back. It's a good read: https://kevinsoffroad.com/blogs/kevi...x-death-wobble

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        • #5
          Ex-XJ owner here. Deathwobble from me started with unbalanced wheels and was coupled with worn suspension--all of the rubber bits were just trashed in the front end. It was not worth the money, time, nor effort to install poly bits, but fortunately after re-balancing the wheels it was back to just being horrible to drive, instead of horrible and scary. I did have a new steering damper and new shocks, which did not prevent the issue. This occurred at effectively stock height; no lift, just a very slightly taller tire. I also wonder if slop in the steering box was part of the issue, but that had been sloppy since new, with an utter lack of center feel in the wheel, and probably 3/4" of movement of the wheel before the Jeep's direction started to change. Made it exceedingly tiring to drive!

          I'm not sure if all XJ's are like that. It was nervous and sloppy and darting on dry, clean pavement, making it tiring and difficult to drive. Put it on gravel, snow, or something otherwise slick and ugly, and it was hands-free stable at whatever speed you felt like going. Very strange.

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          • #6
            My comments would be, the real root cause of death wobble is that cars/trucks are made with lots of attention to body/chassis dynamics, resonance etc. in the vertical plane for highway ride quality, but not much in the horizontal, i.e. side-to-side flex/resonance is permitted by design to be at a low frequency that unfortunately happens to be right about where suspension bushings, tires, springs and all the rest like to cycle. Four-link designs w/ track bar seem especially susceptible to everything getting into a resonance match with a self-increasing amplitude that ends up in wobble.

            All the factory designs are still done well enough that they'll work fine as delivered, but it doesn't take much for things to get right out of whack. Worn parts, suspension lift that puts things at odd angles, larger/heavier tires/wheels with non-factory offsets...all can tip what is a delicate balance.

            Three ways to lessen worry about death wobble on a solid-axle front: One, use a leaf-spring front suspension, they don't seem as prone to it. Number two is, if it's a linked coil sprung style, leave the front suspension and tire/wheel combo stock as designed and have good-condition parts in there. When like many of us your are not going to adhere to either #1 or #2, we come to #3: However you have your front-end done, at completion slide under the front of the car (it doesn't have to be running but it might help to have the power steering working) and have someone rock the steering wheel back-and-forth vigorously, while carefully watching for any odd movement between any set of components as well as any frame flex such as would let the steering box appear to move slightly. Most of the time you won't need to guess at problems if you simply slide under there and look, and if for example there's any little bit of excess movement at, say, the track bar bushing you correct it. If the tie rod ends show looseness get new ones, if the drag link flexes up and down, get a stiffer one. More complicated is, if you see what you'd thought was the rigidly-mounted steering box moving in a non-rigid manner, or if there's any twisting of the frame-mounted track bar attachment if it hangs down below the rail much.

            The link above mentions the three little bolts that hold a steering box on but it ain't the bolts letting the steering box flex around, it's the scrawny little frame they attach through and the steering box braces you can get will help. Stiffer bushings on the track bar can make a difference, but the track bar might need a brace too.

            I had ours to where there was never any wobble under any condition, this with 32" tires and stock rubber-bushed links, then all I did was give the front another inch of lift with some spring spacers and now under very specific conditions it's right on the verge, that's all it took and I imagine it's due to the increased angle on the steering linkage and track bar. If a track bar mount brace doesn't make any difference then the spacers are coming back out, we'll see, it hasn't been a priority lately but will need to be addressed if we start driving it more.

            Dan, on your Sub I'd think you'd be using leaf springs if you switched to solid axle? I have no idea how they did the D44 Pacer but I know those guys who behave like experts tend to sometimes just stick something together without a deeper understanding of what they're doing. Certainly if they've got giant heavy tires on an otherwise-light car, that may work fine off-road but at highway speed it's going to be the tires making the rules and not the chassis. Maybe that's the case-maybe not and keep in mind I ain't the expert either, I'd have to see the video but I'm not subscribed. We do all need to know that when we go to perform major modifications on a frame or chassis, you gotta be ready for anything including seeing that what you thought was a great idea didn't work and needs to be thrown out and started over.

            It would be good to, however you plan to do the Suburban, try to have a way where somebody ahead of you went through all the hassle such as use a kit with good reviews, whatever.
            ...

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            • #7
              I think the cause is play in the steering/suspension, and having the wheels offset too far. I read an analysis of it on the HAMB a while back, but I forgot the specifics....

              I got it on my Barracuda, and tightening up some stuff on the steering made it far less frequent. It's happened 3 times in 1200 miles, and always at low speeds on bumpy roads (ie. conditions where you'd be driving a Jeep)
              My fabulous web page

              "If it don't go, chrome it!" --Stroker McGurk

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              • #8
                Originally posted by RockJustRock View Post
                On a regular car too much Caster does that. Like a shopping cart going too fast.
                Yeah another potential factor, light front ends like lots of caster, heavy not so much, in-between it might take experimentation.
                ...

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                • #9
                  Originally posted by Loren View Post
                  It would be good to, however you plan to do the Suburban, try to have a way where somebody ahead of you went through all the hassle such as use a kit with good reviews, whatever.
                  You mean like this one.. http://offroaddesign.com/catalog/88-...Conversion.htm

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                  • #10
                    Thanks everyone for the comments and opinions. The pacer basically had a XJ susension under it with air bags . It still was a unibody car so it was pretty light sitting on 36 inches I think and probably 12.5 wide . That kit that Tardis listed is one of 4 or 5 companies that I am studying. Leaning toward a company that has both front spring hangers connected . I don't want to get anyone thinking this is going to happen right away as I have a S10 V8 project that needs finished and sold , figure out why the 85 vette that we put another engine in won't stay running more that 5 seconds and figure out the problem on my 92 vette that won't run . Also , there is the choise that needs to be made of just swapping in a ford dana 44 that has the diff on the left side and keep the stock T case but then having to figure out how to get 6 lug rotors on it $$$ to go with my half ton non floater 14 bolt rear or use a chevy front 44 out of the 73 to 87 trucks to go with my 14 volt. Would have a better chance of getting a 3.42 year to match the 14 bolt but then the T case needs changed . Or admit that the gearing is too high for the 36 inch tires and try to get 3/4 or 1 tons to get a matched set with lower gears and bigger brakes . So , alot to figure out .
                    Previously HoosierL98GTA

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                    • #11
                      Originally posted by RockJustRock View Post
                      On a regular car too much Caster does that. Like a shopping cart going too fast.
                      backwards. not enough caster will cause death wobbles or speed wobbles.
                      fixing it needs MORE + caster.

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