Write- Up Diagnosing Death Wobble and Fixing Non-DW Shimmies and Wobbles

Write- Up Diagnosing Death Wobble and Fixing Non-DW Shimmies and Wobbles

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  1. #1
    Forum Tech Advisor planman's Avatar
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    Default Write- Up Diagnosing Death Wobble and Fixing Non-DW Shimmies and Wobbles

    The Inspection Checklist is in Post #2 of this thread.

    Here are a couple videos. The first explains your front end. The second is an actual inspection. You should still read the balance of this post and post #2, but the videos are a good place to start.





    I'll start out by explaining that Chrysler decided to use a 14 mm trackbar bolt, with a trackbar bushing sleeve designed for a 9/16" bolt, and the trackbar bracket bolt holes are somewhere around 15-16 mm large. This is a sure recipe for DW if the trackbar bolts are not properly torqued and periodically re-torqued to 125 ft. lbs.





    Death Wobble is no mystery.

    It is caused by loose bolts, damaged components, or improper installation.

    Look at the picture below and follow along:



    First, the tie rod (green) has ends that attach to a knuckle on each 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 sleeve (in the picture, just to the right of the red swaybar link). That sleeve (maybe not the correct term for it, but you can see what I am talking about) 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.

    Next, look at the drag link (purple). On one end, it attaches to the pitman arm (lavender), 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.

    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.

    Now, imagine that the bolts that hold the trackbar are loose in their bolt holes, or that the bolt holes are wallowed out (oval), or that the bushings at the trackbar ends are damaged, or that the bracket at the axle side has come loose because the weld has broken, or that the bushings are all twisted up because the rig has been lifted without the installer loosening the bolts and then retightened them at the new ride height. 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.

    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, bolt holes, and brackets 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.

    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.

    Next, look at the lower control arms (purple) and the upper control arms (light blue). In the picture, they are aftermarket arms with a heim joint on one end. However, 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.


    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.

    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.

    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.

    Hope this helps--assuming you read it all.

    Death Wobble is no mystery.

    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.




    It is extremely important to immediately diagnose and fix Death Wobble.

    Even one episode of DW can damage other components.

    Multiple episodes of DW are almost guaranteed to damage other components.

    Multiple episodes will often damage your:

    • 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


    Hellbound13 is an example of a member who with 5-6 episodes of trackbar related DW on a stock jeep ended up "chasing his tail" for many, many months. He ended up replacing almost everything in the above list--sometimes more than once.

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




    This is Death Wobble (and the guy is extremely unwise for repeating it on purpose):


    Last edited by planman; 12-02-2013 at 12:11 PM.

  2. #2
    Forum Tech Advisor planman's Avatar
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    DIAGNOSIS CHECKLIST

    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:


    1. Remove the steering stabilizer.
    2. 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.
    3. 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.
    4. Then, I would remove the front trackbar to inspect the 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. If all is good, I would reinstall the trackbar with the tires on the ground at ride height to 125 lbs.
    5. Then, I would inspect the drag link end joints by using a large channel lock wrench 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.
    6. Then, I would inspect the tie rod ends with the channel lock wrench for up and down movement. There should be no meaningful up and down play. There should only be rotational movement in the joint end.
    7. 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.
    8. Then, I would grab the top of the tire with both hands and push it towards the frame and pull it away from the frame to inspect for lateral movement of the top ball joints. There shouldn't be any.
    9. 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 and repeat on the other side.
    10. Then, I would remove the brake calipers and brake disks to inspect the unitbearings for play.
    11. Then, I would reinstall the discs, brake calipers, and tires/wheels and set the axle back on the ground.
    12. Then, I would support but not lift the front axle with a floor jack and loosen the front control arm bolts (upper and lower on the axle side). One at a time, I would drop the 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.
    13. Next, I would inspect the sector shaft that comes out of the steering box for cracking or twisting.
    14. Then, I would take a test drive without the steering stablizer to feel for any wobbles.
    15. Finally, I would reinstall the steering stablizer or spring $40 for a heavy duty steering stablizer.


    If this front end inspection does not diagnose and/or solve it, then I would move to an alignment.

    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.
    2. 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.
    3. I would set my toe-in to spec on the machine--which is about a 1/16"-1/8" toe-in depending on tire size.
    4. If my front to rear alignment is off, I would install rear lower adjustable control arms to fix this.


    Also, I recommend you switch out your stock 14 mm trackbar bolts for 9/16" grade 8 bolts.

    See the following video for more information:



    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:

    • 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.
    Last edited by planman; 01-10-2013 at 10:33 PM.

  3. #3
    Forum Tech Advisor planman's Avatar
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    And, here are a couple videos. The first explains your front end. The second is an actual inspection.


    Last edited by planman; 01-10-2013 at 10:36 PM.

  4. #4
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    Thanks for this...good write up and explanation.

  5. #5
    JK Junkie aldaman's Avatar
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    Thanks for posting. A lot of valuable info
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    *********************

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  6. #6
    JK Freak olyelr's Avatar
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    Wow. A wealth of very important information in this thread. Greatd job on the write-up!
    2016 RAM Power Wagon Laramie

    But I still have love for the Jeep's!

    My locker by-pass write-up http://www.jk-forum.com/jk-write-ups...gs-kit-250203/

    My ESP kill switch write-up http://www.jk-forum.com/jk-write-ups...riteup-260247/

  7. #7
    JK Newbie bobmc's Avatar
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    Hi PLANMAN,

    THANK YOU so much for taking the time to share your expertise on the Jeep Wrangler suspension system. I watched your videos completely, and I belive the world is a better place for having your kind around to share with the rest of us. Since you obviously have a lot of experience with the JK suspension system, I want to ask if you have anything that you can share about the ubiquitous steering column 'knock', or 'clunk' that many Wrangler owners have reported. I see that the lower intermediate shaft part number has been revised a couple of times, finally at 55351281AC, but I have read that even after replacing with the latest revision, people still get the recurring 'knock'. The most popular solution appears to be to grease the boot of the shaft, but that seems like masking the problem rather than fixing it. Is the 'knock' related to death wobble and shimmy? If it's metal-on-metal hammering it would obviously wear eventually. I took my 2009 JK-Unlimited to the Jeep service center and they just want to replace my lower-intermediate steering shaft with the AC revision, but I am not confident that this will solve my knocking issue as they can't explain to me what has changed, or how the new revision would fix it. I've worked as an engineer for around twenty years, so I'd really like to know the problem before I know the solution.

    Thanks again,
    Bob

  8. #8
    Forum Tech Advisor planman's Avatar
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    Bob,

    I've never experienced the knock on either of our 3 JKs.

    The only times I've experienced a knock while looking at other JKs, it was from the frame side front trackbar bolt not being properly torqued.

    What I would do is a steering cycle test like I show in the 2nd video to identify the source(s) of the knock.

  9. #9
    JK Super Freak Rob 12B1P's Avatar
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    Welcome back planman, glad to see this back up again. Definitlely helped a lot of people (myself included) with your work here.

  10. #10
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    Wait so your saying that the bolt should be 9/16?


    If you torque the bolts to the proper specs you won't have the death wobble and the hole won't bore out making it bigger. I don't think Chrysler would put the wrong bolt size in millions of Jeeps without a recall.

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