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Death Wobble and such

ZeroRain

New member
So I got the death wobble on my 95 Cherokee 4.0. Ive been doing my own reseach and all on this and Im starting at replacing my control arm bushings and replacing the track bar bushings because there is no play in the ball joint end. The whole front end is tight and feels good. Now in my research I come across this site, http://go.jeep-xj.info/HowtoAlignment.htm, and its suggesting that the caster could be causing the problem. Per his instructions i put an angle finder on the front diff and instead of being at 2.5 im at 4.5. So that means that my ball joints are straight up and down. What do you guys think? Any info is greatly appreciated.

Zero
 
Without all the information it seems you're measuring pinion angle. The lower your caster angle the more chances you'll have for wobble and other steering problems. Take it to an alignment shop. If it is at +4.5 that is a very good caster angle for a 95. The spec is actually +6 but anything between 2 and 8 shouldn't be an issue. Have you lifted it? Lifts decrease caster and increase pinion angle and also move the axle off center. The factory caster adjustments on the lower control also mess with pinion angle and the service manuals say pinion angle is more important the caster.

95 align specs off alldata
Caster, Deg. +6.0Camber, Deg. 0Toe-In, Inch 0Ball Joint Wear Limit [03]
[03] -- Not available.
 
No lift on this one and it has factory size tires. Im using the pinion to estimate the caster. From what the gentleman on his site said the differential tilt changes the caster. My differential is at 4.5 degrees top forward, and the site mentioned that it should be at 2.5 degrees top forward. So im two degrees too far forward possibly. But its all up in the air until i get the new bushings in.

Zero
 
Is your Jeep lifted, and by how much? It is normal for caster to be reduced as lift is increased, and you can compensate for this some by shimming out the lower control arms at the frame mounts (I'm assuming you have stock, non-adjustable LCAs).

If a line drawn through your ball joints is straight up and down, then you would have zero caster. It would take a lot of lift to lose that much caster, and you would probably need adjustable control arms to correct it, and then you'd have to worry about pinion angles. It would also make the steering really twitchy and dangerous (aside from any death wobble, even). The steering wouldn't have any self-centering force.

If you're not lifted then I doubt you have zero caster. If you do, then something is wrong with your control arms or axle housing. When you look under the jeep at the knuckles you should see a noticeable backwards inclination of the line between the two ball joints (the top joint is further back than the lower).

My guess is that you're not measuring it right. I haven't tried to measure it myself but it looks like it would be difficult to measure with any precision, at least with any tools I have. I'd take it to a good alignment shop and get a printout so you know where you're at on toe, camber, and caster.

Besides, I don't think caster would actually cause death wobble. The self-centering force it gives would help dampen the wobbling, sure, but I don't see how it could start the thing wobbling in the first place. I think DW always comes down to slop somewhere in the suspension or steering. That enables it to wobble, and then something like an out-of-balance tire or a pothole or whatever gets it started, and then the oscillations hit a special frequency that amplifies the wobbling until its uncontrollable.

You didn't mention checking steering components. Have you checked your TREs, ball joints, unit bearings, and steering box for play?

(P.S...just so I'm clear: if you determine that you DO have zero caster, then by all means, you have to fix it. I'm just saying that I think it's unlikely if you're not lifted).

Good luck-

Robert
 
There is no lift, that i know of actually, and no play in the front end. Its all tight as far as i can tell. Ive done the side to side shake with the tires in the air and also the up and down shake. No movement and all is tight. Ive also been under the truck and had a friend move the wheel side to side to try and find movement. I cant see a thing.

Zero
 
Yeah, your caster is probably on the lower end. If your LCA mounts are slotted move them forward. It will bring pinion angle down and caster angle up. Still best to take it to an alignment shop after you get your bushings in. I know you said the front end was tight but did you check the ball joints by putting a rod under the tire and lifting?
 
I have not done the bar. Ive always been taught to grab the bottom of the tire and pull while pushing on the top of the tire. If you feel movement its either ball joints or wheel bearing. At that point get someone to look and see whats slopping.

Zero
 
Hmm, well if you're getting death wobble then something has to be sloppy.

You mentioned replacing control arm bushings; are yours in really bad shape? That can definitely cause DW. When you unbolt the axle end of the track bar to change the bushing, check the bolt hole in the axle. It's been known to wallow out and become oblong. That will let the axle shift a little bit, even if the bushing is tight. That's usually accompanied by a popping noise when you turn, but not necessarily. It would be a source of wobble, for sure.

I replaced nearly everything on the front end on mine last fall because it's got enough miles that I wanted peace of mind (I wasn't getting DW though). I did all the usual tests, but it was really hard to tell what parts were bad until I had them apart. After removing them, it was obvious that both of my lower ball joints were toasted, but I'd never noticed any play when I yanked on the wheel at 12 and 6 o'clock.

The tests where you grab parts and try to wiggle them is useless in my opinion, unless the joint is basically coming apart. Probably the best one for steering components is to have a helper turn the steering wheel back and forth while you watch the joints... but if you just try to watch them all at once you probably won't see anything.

I think it's best to do it with the engine off, using manual force to turn the wheels so everything happens slower. What I do is start at the u-joint in the steering shaft by the firewall and concentrate on it. Stare at it while while it rotates back and forth. Then move on to the next u-joint by the steering box. Then compare the input shaft of the steering gearbox to the pitman arm. Then the end of the pitman arm to the end of the drag link. And so on...the idea is focus on one thing at a time. If you can figure out a way to make reference marks, that can make movement easier to spot.

Good luck, this type of detective work is a pain.

-Robert
 
Wollered out hole hu? I never thought of that one. I just made a 30 mile round trip and was 55 to 60mph and didnt have a single problem. Its also about 12 to 20 degrees colder now then what it was when i originally got the wobble. Im going to wait for the parts to come in and get them replaced and go from there. Ill have the track bar out and hopefully find something.

Zero
 
Alright gentlemen. I did all the bushings and Its still there. Not as bad unless over 60. It Will start at about 55 but stop as soon as i let off the throttle it stops. Im baffled... The only other things to change at this point is the track bar, which has a new bushing and has no play in the ball joint end, and the shocks. The pinion tho is still at 4.5 degrees top forward.

Zero
 
What method are you using to check all the TRE'S and ball joints,same goes for all the bushings?
 
Bushings on the axle im not checking because they are new. The TRE its the 3 and 9 position and then push and pull to try and feal or hear movement. Ball joints is noon and 6, same push pull method. Ive also tried to watch for movement while its on the ground and someone moves the wheel.

Zero
 
Have you done a wheel balance? If you are getting shaking at about 55, that's the classic speed that unbalanced wheels will start to rock your boots off. Easy to test - rotate the wheels front to back, both sides, and take it for a spin to look for a change in feel.

I have had wheel balance bite me from time to time on all of my MJ/XJs. Having lost a weight can produce uncontrollable shaking at about 55 MPH or it can also be a less severe wobble/shake but usually always around the same 55 MPH give or take a few.
 
It doesnt start till you bit a bump with one wheel but not another. then vibes like crazy tills you slow down till 50ish.

Zero
 
It could still be a out of balance wheel. try rotating and go on from there. How's the trac bar joint where it meets the axle? Took me a while to find that one was the problem with mine. My hole on the axle was hallowed out. If it was fine before and no changes were made to suspension then something is worn out... not all of a sudden the pinion angle is causing the DW. You stated the bushings "on the axle are new" what about on the "frame" side of the control arms? There should be 8 total for upper and lower control arms. Is this a new XJ or have u been driving it for a while? More past history please.
 
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Shortly after I had installed my new lift springs I had crazy DW, adjusted the toe.. and still there. Rotated the tires and it was gone. As tires wear they can become un-balanced. Was my issue, could be yours.
 
One of my out of balance episodes was like that - driving at highway speed, hit a small bump or pothole and the whole truck would shake almost out of control untill I was able to slow down. It would then sometimes do it again with an increase of speed, sometimes it was stable again.

Wheel balance was a 100% fix for it.
 
Its brand new to me. All 8 bushing for the control arms are done. The uppers are new arms aswell. The wobble has been there since i owned it and the previous owner started, who had it for a week, said its been there since he had it. The owner before him didnt mention anything or if he did it wasnt relaid to me. When i did the track bar bushing i looked and the hole looks good and round to me.

Zero
 
While I was under the truck greasing everything up I got to looking at the sway bar and the bushings on that thing are toast. I assume this could be another potential cause in the wobble.

Zero
 
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