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Diagnosing Death Wobble and Fixing Non-DW Shimmies and Wobbles (TJ Version)

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  • Diagnosing Death Wobble and Fixing Non-DW Shimmies and Wobbles (TJ Version)

    [SIZE=2]Death Wobble is no mystery.[/SIZE]
    [SIZE=2]It is caused by loose bolts, damaged components, or improper[/SIZE]

    [SIZE=2]Look at the picture below and follow along:[/SIZE]

    [SIZE=2]First, the tie rod (yellow) has ends that attach to a knuckle on the driver side and the drag link on the passenger side. As you could imagine, if either ends of the tie rod were broken or bad, that could be a culprit for a shimmy (not Death Wobble). A common place to damage the tie rod is on the driver's side at the adjusting collar (not in the picture). That collar/sleeve allows the width of the tie rod to be expanded or contracted. There are threads on that end that can be damaged, causing play on that driver's side and allow an up and down, or circular play movement. Again, this would cause a shimmy, not Death Wobble.[/SIZE]

    [SIZE=2]Next, look at the drag link. On one end, it attaches to the pitman arm (light green), that attaches to the steering gear box. On the other end, the drag link attaches to the passenger side knuckle. When you turn your steering wheel, a shaft turns that goes to the steering gear box. The steering gear box turns the pitman arm, and the pitman arm pushes or pulls the drag link, which pushes or pulls the knuckle. Your steering wheel is straitened by loosening the two nuts on the sleeve/turnbuckle on the drag link and rotating the sleeve/turnbuckle to lengthen or contract the length of the drag link. If either end of the drag link is damaged, this would cause a wobble or shimmy, but not Death Wobble.[/SIZE]

    [SIZE=2]Next, look at the trackbar (aqua). It attaches to a bracket on the frame on the driver's side and to the axle on the passenger side. The purpose of the trackbar is to center the axle on the frame. With the axle centered on the frame, it provides some resistance to the steering system to allow you to turn. If there was no trackbar and you turned the steering, the whole front frame would shift. As a result, there is significant force applied to the trackbar in driving and steering. [/SIZE]

    [SIZE=2]Now, imagine that the bolt and end that holds the trackbar are loose in their bolt holes, or that the axle side bolt holes are wallowed out (oval) and the end at the frame side is damaged, or that the bushings at the axle side trackbar end is damaged, or that the bracket at the axle side has come loose because the weld has broken/cracked, or that the axle side bushing is all twisted up because the rig has been lifted without the installer loosening the bolt and then retightened them at the new ride height and the bracket has pinched the bolt sleeve in the bushing at a different ride height--twisting the sleeve away from the bushing. All these things would allow play in the front trackbar. When you steer or go around a corner, these loose or broken things would allow the axle to shake or slide side to side. If you hit a bump in the road, it could knock the trackbar towards the driver's side. Then, the rest of the suspension (springs, etc.) would try to bring the trackbar back to the passenger side. If you were going at any sort of speed, you could develop a kind of harmonic resonance as the axle more and more violently slide/rocked/shaked from side to side. It would feel like your whole front end was being voilently torn apart. You would have to bring your vehicle to a complete standstill to stop the harmonic resonance. This is Death Wobble.[/SIZE]

    Also, look at the picture of how the frame side of the trackbar has something similar to a tie rod end. When the suspension droops in a TJ or XJ, the design of the frame side ends binds the end and can damage or break the end--leading to the scenario described above.

    [SIZE=2]Even one incident of violent Death Wobble related to the front trackbar can cause significant damage. The voilent harmonic resonance of the back and forth shaking is more than the trackbar bushings, trackbar frame side end, bracket bolt holes, and brackets and welds are designed to handle. A severe Death Wobble occurance can crack or break the welds on the axle side trackbar bracket, or the bolt can wallow out the bolt hole in the bracket, or the bushing can be permanently damaged.[/SIZE]

    [SIZE=2]This is the most common source of Death Wobble because inexperienced installers either do not remove the bolt from the trackbar when they install a lift--leaving the bushing pinched in the bracket and bound up, or they do not properly torque the bolts after the lift has been installed with the tires on and the full weight of the vehicle on the ground at ride height, or (maybe the most common) they do not retorque the trackbar bolts after the first 50 miles, after every heavy wheeling trip, and at every oil change interval.[/SIZE]

    [SIZE=2]Next, look at the lower control arms (orange) and the upper control arms (purple). In the picture, they are stock arms. The stock control arms have a rubber bushing at each end. When the control arms are properly torqued, the bushing is somewhat pinched in the mounting brackets on the axle and the frame. Sometimes, an installer will make the mistake of not loosening the bolts for the control arms when they install a lift. What happens sometimes is they really bind up the bushings because they are pinched/sandwiched at stock ride height, but then forced to the new lifted ride height. These bound up bushings can cause weird handling, bushing failure, and lead to Death Wobble. The proper way is to loosen the bolts, install the lift, reinstall the wheels so the suspension and jeep are at the new ride height, rock the vehicle/suspension back and forth and side to side, then re-torque the bolts to spec, then after 50 miles re-torque them to spec, then after every oil change or very heavy wheeling trip re-torque them to spec.[/SIZE]

    [SIZE=2]Improperly balanced tires, too much air in tires, bent wheels, improperly installed wheel spacers, bad tires (with separated plys), and poor alignment specs (caster, camber, and not enough toe-in) can cause wobbles and shimmies that lead to Death Wobble. However, these precipitate Death Wobble, but they are not the cause of Death Wobble.[/SIZE]
    [SIZE=2]Although not specifically identified in the picture, the ball joints that are at the top and bottom of each knuckle where it attaches to the axle C can go bad. Bad ball joints can cause shimmies, wobbles, but usually not full on Death Wobble.[/SIZE]

    The swaybar links (red) have bolts that can work themselves loose. This also can lead to bad wobbles.

    [SIZE=2]Next, allthough not identified in the picture, the unit bearings can go bad and be a cause of shimmy and wobble, but not Death Wobble.[/SIZE]

    [SIZE=2]Hope this helps--assuming you read it all.[/SIZE]

    [SIZE=2]Death Wobble is no mystery.[/SIZE]

    [SIZE=2]The reason that the steering stabilizer masks it is that it can absorb some of the side to side voilent harmonics of a loose trackbar or damaged mounts. However, this masking is dangerous because it will not prevent the eventual failure of trackbar bracket welds and bolt holes from trackbar Death Wobble.[/SIZE]

    [SIZE=2]It is extremely important to immediately diagnose and fix Death Wobble.[/SIZE]

    [SIZE=2]Even one episode of DW can damage other components.[/SIZE]

    [SIZE=2]Multiple episodes of DW are almost guaranteed to damage other components.[/SIZE]

    [SIZE=2]Multiple episodes will often damage your:
    [LIST][*]ball joints[*]tie rod ends--including the adjusting sleeve end on the driver side[*]trackbar bushings[*]trackbar bracket bolt holes[*]steering sector shaft (where the pitman arm attaches to the steering box)[*]steering stabilizer[*]front lower control arm bracket bolt holes[*]unit bearings[*]trackbar bracket welds[*]drag link ends[/LIST]There are many, many examples of jeepers who with 5-6 episodes of trackbar related DW even on an a stock jeep have ended up "chasing their tails" for many, many months. It is not uncommon for people to end up replacing almost everything in the above list--sometimes more than once chasing sources of DW and non-DW wobbles and shimmies.[/SIZE]

    [SIZE=2]Without repairing/replacing everything that was damaged at once, the remaining damaged components continued to cause DW problems, further damaging the remaining components.[/SIZE]

    [SIZE=3]This is Death Wobble on a JK (and the guy is unwise for repeating it on purpose):[/SIZE]
    <strong><font size="3">

  • #2
    Re: Diagnosing Death Wobble and Fixing Non-DW Shimmies and Wobbles (TJ Version)


    Assuming your tire psi is 28-30, your tires/wheels have been balanced and rotated to make sure the wobble doesn't move with the rotation, here would be my order:

    [LIST=1][*]Remove the steering stabilizer.[*]Have someone turn the engine on and turn slowly from full lock to full lock while I visually, manually (with my hands on the components), and auditorily inspect for any play in the tie rod ends, drag link ends, sector shaft, trackbar ends/bolts/brackets, and trackbar bracket welds.[*]Then, do the same thing but with short, sharp, quick back and forth turns of the steering wheel between the 10 o'clock and 2 o'clock positions, instead of the slow, lock to lock approach.[*]Then, I would remove the front trackbar to inspect the axle bracket bolt holes for ovaling and inspect the trackbar bushings for separation or cracking with a long screw driver through the bolt sleeve and the trackbar in a vise to leverage against the bushing in all directions. I would also inspect the frame side bracket for damage and the frame side end of the trackbar for up and down play using a channel lock pliers. If all is good, I would reinstall the trackbar with the tires on the ground at ride height to 55 lbs at the axle side and 65 lbs at the frame side.[*]Then, I would inspect the drag link end joints by using a large channel lock pliers that gave me enough leverage to check for up-and-down play in the drag link ends. There should not be any meaningful up and down play. If there is, the ends should be replaced, or a new drag link with heavy duty joints should be installed. After, I would check the torque of the drag link ends. Taller lifts magnify the problems of bad drag link ends.[*]Then, I would inspect the tie rod ends with the channel lock pliers for up-and-down and in-and-out movement. There should be no meaningful play. There should only be rotational movement in the joint ends.[*]Then, I would put the front axle on jack stands with the tires about 2" off the ground and check the front ball joints by using a long pry bar as a lever under the front tires to lift them up to inspect for up and down play in the lower ball joints. There shouldn't be more than maybe 1-2 mm.[*]Then, I would use the prybar/lever against the frame or just my hands on the top and bottom of the tire to inspect for lateral movement of the top ball joints. There shouldn't be any. If you have a lighter tire/wheel combo, you can do this by hand.[*]Then, I would remove the front tires/wheels and remove the front tie rod--one knuckle at a time. Then with a large wrench or vice grips, I would inspect the end for side to side play. Then I would reinstall the end and torque to spec (20 ft. lbs.) and repeat on the other side.[*]Then, I would remove the brake calipers and brake disks to inspect the unitbearings for play.[*]Then, I would reinstall the discs, brake calipers, and tires/wheels and set the axle back on the ground.[*]Then, I would support, but not lift, the front axle with a floor jack and loosen the front lower control arm bolts. One at a time, I would drop the lower control arms to inspect the bolt holes and bushings (similar to with the trackbar), reinstall without torquing, and do the next one. Afterwards, remove the floor jack so the suspension is at ride height, vigorously rock the vehicle side-to-side and front-and-back, then torque to spec. (LCAs frame side 130 ft lbs, LCAs axle side 85 ft lbs, and upper CAs 55 ft lbs.[*]Next, I would inspect the sector shaft that comes out of the steering box for cracking or twisting of the splines.[*]Then, I would take a test drive without the steering stablizer to feel for any wobbles.[*]Finally, I would reinstall the steering stablizer or spring $40 for a heavy duty steering stablizer.[/LIST]If this front end inspection does not diagnose and/or solve it, then I would move to an alignment.
    [LIST=1][*]I would use adjustable lower front control arms to set my caster spec between 4 and 5 degrees--with a cross caster that has less on the driver side than the passenger side. I would personally not do more or less, with a target around 4.5-4.7 degrees caster.[*]If my camber is out of spec, but it is not due to failed ball joints, I would install offset ball joints to get my camber in spec.[*]I would set my toe-in to spec on the machine--which is about a 1/16" to 1/8" toe-in.[*]If my front to rear alignment is off, I would install rear lower adjustable control arms to fix this.[/LIST]With all this, I highly doubt you do not find the source.

    The last ditch thing if there is a non-DW, speed dependent range wobble, I would borrow a different set of wheels and tires to see if it changes, and I would try driving it with no front driveshaft to see if that changes anything.

    Although it is always a good idea to inspect your axle shaft u-joints, they will not cause DW.

    The most common sources of full on DW are:
    [LIST][*]Improperly torqued trackbar bolts[*]Damaged trackbar and control arm bushings because bolts were torqued on a car lift or while the vehicle was not at ride height with the tires on the ground. When you torque trackbar and control arm bolts, the bracket pinches the bolt sleeve in the bushing, as well as the bushing itself. If this is at a geometry other than actual ride height, the bushings are twisted/bound/pre-loaded, and they will eventually fail/separate/etc. If you have a flex joint end, this does not apply for that end.[*]Ovaled out trackbar bracket holes due to DW episodes from loose bolts.[/LIST]


    • #3
      Re: Diagnosing Death Wobble and Fixing Non-DW Shimmies and Wobbles (TJ Version)

      Great to see you and your write up here. I think it'll be great to be able to direct people to a forbidden post instead of sending them elsewhere to read your write up.
      '09 JKUR, 35" Nitto TG, Home built winch bumper, custom built sliders, MetalCloak Overlines, RockHard engine/trans skid, RK HD Pro Tie Rod, RK HD drag link, spiderweb shade, TF 3" LA, Adams Front shaft, Warn M8000
      [COLOR=#ff0000][FONT=arial black]I.Y.A.A.Y.A.S.[/FONT][/COLOR]