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Causes of death wobble?

blistovmhz

NAXJA Forum User
Location
Vancouver, BC
Okay, this question has been killing me for years, but because I've never experienced it, I've never asked. As I just haphazardly lifted my 98 XJ another 2" from 4.5-6.5", on my gravel driveway, in the rain, and I'm headed out on a trail run in a few hours, I figure now's the right time to ask (or like, 2-3 days ago).

What causes death wobble? I understand the concept but haven't ever seen it despite my numerous hacky lifts I've installed/built over the years. Some of the causes, such as worn/loose suspension components or poorly balanced tires or drive shafts, but I hear a lot of guys talking about poor alignment causing it, and I just don't understand this. Lots of people talk about setting the caster on each side individually but this doesn't make sense as the knuckles are welded at whatever angle they're welded at. I've heard guys telling people to set the caster of one side by preloading the control arms but this doesn't make sense as it means destroying your bushings. Same goes with camber. I've heard guys say it can change with a lift, but this makes no sense to me as I haven't changed the ball joints.

The reason I ask now is that after the lift, I sit about 20' in front of my Jeep and look at it head on and the drivers front wheel looks like it has a lot more camber than it should. It also looks toed out, but I've measured at several different points, drove forward to rotate and measured again and I'm always 1/16th in. Perhaps some sort of optical illusion caused by driveway slope combined with increased bumper clearance thus increased visibility of the front end? I dunno. Jeep was in for OOP VI a few months ago and they set my toe then, and I don't see how lifting it would cause the toe to change anyhow (unless the caster was way out of whack).
When I took it for a quick (low speed) test drive, the steering felt a little floaty. I know most guys will say that's a consequence of lift, but my 4.5", even with worn bushings and lose bolts, felt stiffer.

But, camber, as far as I understand solid axles and the mechanical properties of a steel straight axle, can't be adjusted without swapping out your ball joints or bending the axle right? I'm not concerned if the axle is bent because if it is, I've been driving it like that for 2 years and it doesn't seem to mind. With the old short arm (non-adjustable) RE kit, the front axle was clearly too far back, angles were horrible, but it drove fine. Only reason I swapped it out was because the control arms were too short for the lift and caused the coils to bow forward and run into other components when flexed, and all the bushings were destroyed due to improper (drunk) installation by the previous owner.

But, when I look at the front, that drivers wheel looks to be cambered in by at least 2 degrees more than the passenger side which looks almost straight.

Is there anything I could have done with the long arm installation that could cause increased camber? I can't think of anything.
Should I be worried about DW on my trip today, or is this just post-hacky-installation paranoia?

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"Looking" at your alignment tells you very little. Have the alignment checked and get a printout of the results.

If one tire is tilted, and has uneven tread wear, I would suspect a faulty ball joint.


DW is not usually caused by one single item on the list below, it occurs when a combination of weak, damaged, failed, or out of specification items on the list are present. Tire issues will only initiate DW, and are not the sole cause of DW.

List of almost everything that can cause death wobble:

-Front alignment out of spec
-Loose track bar
-Worn track bar bushings
-Worn track bar end
-Needing an adjustable track bar
-Bad bushings/joints in control arms
-Worn/damaged steering stabilizer
-Worn/damaged shocks
-Worn/damaged tie rod end
-Bad U Joint
-Bad ball joint
-Loose frame side control arm or track bar mount
-Worn or damaged axle side mounting bracket
-Steering box looseness
-Bad front hub assembly
 
Jack the tire off the ground and grab it by the top/bottom, see if you can move it in and out. How old are the lower ball joints? With big tires, these things seem to eat lower ball joints (even spicers) every few years. Also, make sure the track bar mount, track bar bolts are tight. Make sure everything is tight. Like Tim said, it's usually a combination of worn parts, and an out of round/balance tire can kick it off.
 
deathwobble can also be cause by the caster angle being out of whack after a lift, i put upper control arms that were too long on my xj and it was terrifying over 20mph.
 
Agreed, worn out ball joints. Before I threw a real lift on my XJ, I got to experience both death wobble and bumpsteer on the crappy 3'' lift kit that was on it when I bought it... Death wobble was caused by worn out ball joints and the bumpsteer was caused by a bad track bar mount.
 
Was caster angle. RC's instructions tell you to set the CA's to a certain length during installation but recommend getting an alignment done after. As I'm in Canada, there aren't any shops capable of a proper alignment. *sigh*. Ryan from RC knew what the problem was immediately and told me to pull the UCA's back a few turns. Brought it to 87.5 degrees (measured at the diff cover bolts) and everything seems better. Not pulling left and doesn't feel skakey.
 
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