How To: Fix Death Wobble

Ill try to make this as simple as possible, this is yet again an attempt to eliminate some of the repeat questions.

First, what causes death wobble?

Theres a number of things that can contribute to it, but there is a couple that top the list. This list is in order of most common to least common causes.

1. Track Bar mounts, upper and lower.
2. Caster/Camber
3. Wheel Bearings
4. Allignment
5. Tire Balance
6. Tie rod ends/drag link

Now on how to fix it all, Ill try use diagrams when I can.

1. Just tighten the lower axle mount and the upper frame mount. What usually happens is the bolt will either become loose, or the bushing will go bad. Most commonly happens when a used track bar or a stock one is being used with alot of lift (5"+).

2. Heres one thats overlooked alot when lifting a 4 linked vehicle. (thats your suspension type) In the diagram, the red line is your outer knuckle, if it is not within .08* of center on a 90* level, you will get an over toe either in or out.



3. These are also known as unibearings, there the wheel mounting surface (WMS) for the front axle, they then mount to the knuckle. If these go bad there is an easy way to check. Jack the axle up so the tire is no longer in touch with the ground and push/pull the tire in and out from top to bottom. If theres a little play it is going bad, usually 1-2 cm, if theres alot of play, 1-2 in it is bad and needs replacing. They will go bad, its not a matter of as is when. With tires 32"+ its a common headache. You can get pretty decent replacements at any parts store for around $150 ea.

4, and 5 are pretty self explanatory, maintain your rig and take it to the tire shop.

6. If you didnt already know, even with a drop pitman arm, the joints on your steering will go bad. The drag link is the biggest PITA due to it only having 1 replaceable joint on the pitman end. The rest of the draglink has to be replaced to fix the lower mount. Tie rod ends (TRE) are fairly cheap at around 30$ or so a pop. There is a fix for the draglink. Cut the outer joint off. Take another draglink, unscrew the turn buckle style adjustment. Cut the turn buckle in half. Weld the unthreaded end to the cut lower end of the draglink. Now you are able to replace both ends without spending 160$ at a time to replace the whole thing.

If theres something I missed add it.

Brian

control arm bushings

What should the correct castor / camber be on a lifted XJ?

ZachMan said:

What should the correct castor / camber be on a lifted XJ?

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Adjustable Control Arms, if the arm is too short it will pull the bottom of the axle in and rotate the top of the axle forward.

88rockxj said:

control arm bushings

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Ive run some pretty bad bushings without replacing them and havnt had that one happen or hear of it yet. But thanks for the input....

For a stock XJ (from a 2000's manual)
ANGLE___________PREFERRED__RANGE_________MAX RT/LT DIFFERENCE
CASTER__________+ 7.0°____+ 5.25° to + 8.5°_________1.25°
CAMBER(fixed)_____− 0.25°__- 0.75° to + 0.5°__________1.0°
TOTAL TOE-IN_____+ 0.25°____0° to + 0.45°___________.05°
THRUST ANGLE_____0° +/- 0.15°

Caster is ok if it's over 2 degrees, but if you have other instabilities, you'll need more caster to retain stability.

Camber won't change, but if its way off then you have something to replace, like a ball joint or two.

toe in should be just the slightest bit (1/4" narrower at the front) if you have stock steering, but closer to 0 if you have lower-tolerance joints (eg heims)

Badcop said:

Adjustable Control Arms, if the arm is too short it will pull the bottom of the axle in and rotate the top of the axle forward.



Ive run some pretty bad bushings without replacing them and havnt had that one happen or hear of it yet. But thanks for the input....

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it will cause true death wobble, not just wheel shimmy which most people label as death wobble.

will both tires shack from left to rigth with death wobble?at the moment my 91 xj is doing this do to a 1 gallon empty milk jug flying out of someones car dont ask why but the dam thing hit right behind my right tire soon there after i had a mild shimmy of left to right on both my tires now at a bout 15mph i can look down my hood and see the move ment. what could have caused this? the items listed above? and if so which one is likly the cause? also howl ong can i drive before it will damage anything else if it will damage anything else the tires are already worn so im not worried about un even wear lol. thanks for the help

Id start by ensuring all your suspension hardware and components are torqued to specs. Then, start with your alignment checking your tow and caster. If that doesnt solve it, have your tires ballanced. If that doesnt do the trick, id take a look at your tierod ends.

After i did my lift, i had a NASTY case of death wobble at any speeds over 30 MPH. Turned out it was a toe in issue. I adjusted the toe to factory recomended specs and VIOLA...no more death wobble. Sometimes, you just get lucky!

well my jeep isnt lifted its a stock xj. but should i still check all of those even if its not lifted

jeepster89 said:

well my jeep isnt lifted its a stock xj. but should i still check all of those even if its not lifted

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Most definetly...especially more torwards the worn parts or out of ballance tires since its not lifted. Most serious changes in alignment that would cause death wobble are created by lifts or serious impacts(huge potholes, accidents, etc but can also be the cause of more serious problems) to the driveline and since im assuming you have neither, id start looking at worn tracbar parts, tie rod ends, out of ballance tires, etc.

kubtastic said:

toe in should be just the slightest bit (1/4" narrower at the front) if you have stock steering, but closer to 0 if you have lower-tolerance joints (eg heims)

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This is true...although that 1/4" value is dependent on tire size. A better measurement if you're able to do it is the angular difference, like that .5* given on the spec sheet.

The reason this is done, is because due to road force acting on the tires, it'll try and push the tires apart from each other. That 1/4" of toe-in allows for road force to take up any slack in the joints, and also stress the tie-rod and draglink connections. The reason you can go less with better hardware is because there's less room for expansion, and since the ideal setup is straight, you want to keep it as close to that as possible.

I've found that sometimes toe-in can help with directional stability, but this is primarily the job of the caster angle, and as such an improper amount of toe-in often means that other settings are out of spec as well.

To answer ZachMan's question, regardless of the lift on your vehicle, you want to try and keep things true to the factory specs as far as alignment is concerned. In fact, it's probably even more important to keep it true than it is with stock tires, because there's a lot more stress on the steering and axle location pieces with larger tires.

Good thread...my first experience with DW was indeed caused by a loose trackbar bolt, and improper caster. The second (and only other) experience was caused by something not on the list, which was badly worn tires. If you tires have a severe wear pattern which results in the tire contact patch not being even with the road, or you've worn them to the point where the cords are showing (like in my case), you can get unequal road force between the two steering tires and get some DW as a result. In this case, rotating the tires is a good way to check this as a cause, but you'd probably want to just replace them anyway. Which I did.

ok ill deff look into this stuff and if i took it to get an alingement(sp?) would they be bale to tell me what is wrong with it?

also on toe-in: if you use the 242's full-time 4wd option, I think the factory spec is 0 toe-in.

kubtastic said:

also on toe-in: if you use the 242's full-time 4wd option, I think the factory spec is 0 toe-in.

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That sounds like it could be true, I imagine they'd like the front wheels to be pulling in the same direction as the rear.

vetteboy said:

although that 1/4" value is dependent on tire size. A better measurement if you're able to do it is the angular difference, like that .5* given on the spec sheet.

The reason this is done, is because due to road force acting on the tires, it'll try and push the tires apart from each other. That 1/4" of toe-in allows for road force to take up any slack in the joints...

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vetteboy said:

regardless of the lift on your vehicle, you want to try and keep things true to the factory specs as far as alignment is concerned. In fact, it's probably even more important to keep it true than it is with stock tires...

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"1/4" toe-in"???
"keep true to factory specs"???

seems to be a conflict here.

in any case, if you need a 1/4" to compensate for slack, fix the slack

DIY alignments and checks will likely be done with a tape measure: 1/8" narrower in the front will yield about 0.22* toe in, and 1/4" will do about 0.45* toe-in.

For 0.5*, the jump from a 27" to a 35" tire is an additional 0.05" inches (a 20th of an inch) of toe-in when measured as the difference between the leading and trailing spans between front tires.

angle of toe-in is approximately: tan(toe-in distance / tire diameter)*180/PI.

MaXJohnson said:

"1/4" toe-in"???
"keep true to factory specs"???

seems to be a conflict here.

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Really? Where?

I said the 1/4" is dependent on tire size, whereas the factory recommended value is given in degrees. Kubtastic's last post shows the relation between the two, and in fact shows that 1/4" of toe-in at most tire sizes gives you values within factory spec. Where's the conflict?

'Slack' involves more than just worn rod ends. It's also the effect of road force on steering links and geometry, both in terms of tensile forces and tolerance in even brand new joints. The 'fix' as you put it, is to run higher-tolerance steering gear, such as higher-thickness DOM links and heim joints, which you can see gives a smaller toe-in value anyway.

Looks like you need to read a little closer.

stock inverted-Y is another oddity - toe-in changes a little as the suspension cycles.

Yep, exactly, which is why you should do an alignment after doing any suspension changes. If you do it with the wheels off the ground, you should have the axle supported on jackstands taking the full frontal weight of the vehicle.

kubtastic said:

DIY alignments and checks will likely be done with a tape measure: 1/8" narrower in the front will yield about 0.22* toe in, and 1/4" will do about 0.45* toe-in.

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Thanks for adding that, I like to do a driveway allignment every couple of days for a week or so after any suspension mods, while driving it it allows everything to loosen and settle till you get it within a 1/8" of true.