Diagnosing Death Wobble and Fixing Non-DW Shimmies and Wobbles
The videos are kind of long at 18-19 minutes each. Hopefully, they are thorough enough to help.
Death Wobble Diagnosis and Inspection Jeep JK Wrangler Part 1 - YouTube
Death Wobble Diagnosis and Inspection Jeep JK Wrangler Part 2 - YouTube
Inspection Checklist is in Post #2.
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.
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Death Wobble is no mystery.
It is caused by loose bolts, damaged components, or improper
installation.
Look at the picture below and follow along:
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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:
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 foolish for repeating it on purpose):
YouTube - Death Wobble
Death Wobble Diagnosis and Inspection Jeep JK Wrangler Part 1 - YouTube
Death Wobble Diagnosis and Inspection Jeep JK Wrangler Part 2 - YouTube
Inspection Checklist is in Post #2.
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
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 foolish for repeating it on purpose):
YouTube - Death Wobble
2
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Following up on this, a separate thread with some good pics and so on has developed on replacing these bolts. You can find it here.I do not recall where I read it, but I understand that nylock nuts do not give accurate torque spec readings due to the resistance from the nylon. This might be fine for armor, but I would be hesitant to use them with suspension components.
It would be best to use stover top lock nuts. However, I understand that a nut with a lock washer would be second best.
Poly Performance sells a grade 8 hardware kit for the JK:
Poly Performance JEEP/TRUCK & BUGGY*::*Suspension*::*Suspension & Lift Kits*::*Jeep Suspension Systems*::*2007-Current Jeep JK Wrangler Suspension Systems*::*Synergy Suspension*::*Synergy Suspension Jeep JK F911 Hardware Kit - 4X4 Off-Road Parts, JK
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It replaces all the hardware in all 4 lower control arms and both trackbars.
Description:
High strength F911 hardware
Replaces the Lower Control Arm (LCA) hardware that gets destroyed from wheeling abuse
Replaces the Track Bar (TB) bolts which often get worn out from service
Includes hardened extra thick washers that will not deform or contort like standard washers
Kit Includes:
(8) 9/16-18 UNF x 4.0" long F911 bolts (LCAs)
(4) 9/16-18 UNF x 3.0" long F911 bolts (TBs)
(12) 9/16-18 UNF G9 Stover top lock nuts
(24) 9/16" Extra Thick G9 hardened flat washers
It may seem steep at $65, but it isn't easy to find the Stover top lock nuts in smaller quantities.
If you ordered 25 Stovers at $20, and then spent $2.25 each for the 8 bolts that are 4" long, $2 each for the 4 that are 3" long, and $0.50 each for 24 extra thick washers, you'd spend $58 gathering the hardware yourself to save $7.
Although the front trackbar is the one of biggest concern, it would definitely not hurt to upgrade the hardware for both trackbars and all 4 lower control arms.
I don't quite see the logic here.Frogy said:
Unless they're lock-tited or welded in, bolts loosen in all sorts of applications. Maybe they weren't torqued enough to begin with, maybe they were put through undue strain or flexion, maybe they were defective, etc.
The suspension system is held together by bolts. Sometimes one or more of them loosen. That's made more likely when some of those bolts should have been shouldered to prevent unnecessary wear, but wasn't.
Maybe I'm missing your argument.
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