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The ol' death wobble

xjklmnop69

NAXJA Forum User
Location
MI
I did many searches with no ultimate luck

99' XJ with 6" lift. Dana 30 high pinion. Lift is made up of 3" springs and 3" spacers, fixed tubular lower control arms, OG uppers, rubicon express adjustable track bar with bracket/brace.

I had a weekend in the sand dunes then drove home about 300 miles at 80 mph. Washed it off then didn't drive for a few days only to get a death wobble. Since then I've gone through trying to find the "part" that started the whole issue.

As of now, the upper and lower ball joints are new and tight. Upper and lower control arm bushings are new and crack free. Tie rod ends, drag link and pitman arm all new and tight. New wheel bearings both sides. The track bar bushing is poly and good. Johnny joint is tight and hard to articulate.

The tires are new, balanced and passed alignment specs

For the most part, she drives smooth and straight until a bump is hit when going over 45 mph. Some bumps hit both tires others just a single side but both send it into a shaking resonance until you drop the speed down to about 30 mph. Doesn't always happen but usually on a few known bumps. When she wobbles it pulls hard right

I'm out of ideas. I can't find anything loose or worn. Any help would be appreciated
 
I'm thinking you have almost no caster. 6" is quite a bit of lift for stock/short arms.

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Does steering drop match track bar drop.

Usually I wouldn't suspect the brand of pressure washer being used but this time washing appears to have instantly causing death wobble.

I'd dig into track bar drag link geometry before spending any money. If mine id get rid of half the lift to

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In March, I was driving from my house up to the in-laws. 50 mile drive maybe? I was going 65-70 on the interstate until maybe 15 miles to go, got a hit of the wobble and finished the interstate portion going 54.

So I’d say, it can sometimes be just that fast.

Get with your life partner/friend/child/neighbor and have them turn the steering wheel back and forth while you have your hand on the steering linkage, panhard, ball joints, feel for anything moving at all. Replace. Repeat.

Jack up one axle end, wiggle the wheel (it shouldn’t wiggle), replace parts as needed.

Report back with closure.
 
According to the alignment sheet, I have 7.8 and 7.7 degrees of caster. I threw an angle finder on the top ball joint and got ~8. The setup work for fine on these same bumps for 8-10k

Initially I thought I threw a wheel weight during the wash but wheels were still in balanced. I swapped wheels around corners and asked the tire shop to confirm.

The track bar center line is about 2 inches lower than the pitman arm. I know i've pushed the stock geometry limits so I had tried a drop pitman arm but it did not help with the shake. The drop arm put the drag link connection an inch below the track bar. Axle side have stock locations. At this time I had also tried lowering the front by swapping back in a 2" coil spacer I previously used but still had the same shakes

I didn't have anyone to help me tug it around tonight so I set up camera. Doesn't appear to have any loose connections. Tie rod ends, ball joints, track bar ends, control arm mounts. Jacked up each wheel, no 12-6 o'clock movement and only 3-9 until the steering column locked up. Then I stuck a 6 foot pry bar under each tire and a stack of wood; ball joints don't move with me bouncing on pry bar end.

Thanks for the quick replies. I'll get a helper to turn the steering wheel for me tomorrow. Hopefully feel something different

Oh and i've also checked all the mounting holes to see if they've ovaled out from loose bolts. They all look round and all bolts were tight
 
My vote is the poor geometry and the caster not being in the sweet spot, and/or loose tracbar bushings. What's always worked for me is to point the pinion at the front t-case output and see how that drives (probably poor) and then keep adjusting the pinion lower and lower until it drives nice but you don't have any driveshaft vibes. Also, get a control arm drop kit on there. Will make a world of difference.

Edit- Ahhh. You don't have adjustable control arms... Get some adjustable uppers/lowers and a control arm drop kit on there, or drop the lift back down to 3'". That thing must ride like a dump truck.
 
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That alot of castor for 6" lift.
Hows pinion angle?

Drag link and track bar have to be parralell doesnt matter if they are at a different elevation.

Death wobble is an extreme toe in toe out situation springing through the front end and transmitting through to the rear bumper.

This can be kicked off by any thing from nad shocks-out of balance tires. However it often is found track bar itself or steering is culprit exspecly lifted rigs with stock steering.
This steering by design has a small amount of toe change as suspension cycles. This paired with funky angles not being parralell can cause it.

Definitely read on this topic the more you understand the more your likely to fix the problem and tune your jeep

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I agree with most of what I read.

6" with 3" spring, 3" spacer, and no drop bracket is old school.
OK for the trail, but not optimal for the street. Harsh ride and poor geometry are the highlights of that kind of lift. Also, the 3" spacer, is like a poor man's bump stop; you will limit your up-travel to what the spring can compress to, which is also hard on the spring.

If you want to stay at 6", you may want to either move the mounts back, like in a long arm setup, or use drop brackets to get the geometry under control. Then consider revising your spring set up to full length coils. The last XJ I had at 6" had long arms, and no issues other than it handled like a circus wagon.

As DW can be caused by anything from wheel balance to worn components it can be problematic to find/locate. My 1st thought after seeing that the problem showed after trip to sand country was sand in the wheels. You didn't mention your steering setup. The stock XJ steering rods are great for the XJs original mission, but with larger tires act like a spring. If you haven't upgrades, consider a ZJ setup, they are fully swapable, and is a solid arm. Tire sizes are also a huge factor. Up to a 33X12.5 shouldn't cause much of an issue, but above that the sidewall is a bit flexible and I've seen a lot of folks in that size with DS they can't fix.
 
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Make sure you check the steering gear box and the frame around it. Also, check the steering gear box spacer. I take it you upgraded to a steel one.
 
was your alignment checked before or after the dunes trip? the dunes can be pretty rough on stuff... the stock tie rod and upper control arms are pretty flimsy stuff. ive seen then bend with light abuse from wheeling or romping at the dunes. still... bad toe or castor will manifest itself as wondering or poor return to center, not specifically death wobble. the trackbar/drag link angles mentioned above will result in bump steer, again, not specifically death wobble.

if everything new and tight, there are still 2 things i think worth checking... the steering box spacer, as mentioned above. also, the track bar bolt on the axle side. the mount is pretty thin sheet metal. even with the bolt being tight and the joint in good shape, the hole tends to wallow out, allowing slop. both this and the frame side steering gear mount can be quickly checked with a second set of hands moving the wheel, as described above.
 
was your alignment checked before or after the dunes trip? the dunes can be pretty rough on stuff... the stock tie rod and upper control arms are pretty flimsy stuff. ive seen then bend with light abuse from wheeling or romping at the dunes. still... bad toe or castor will manifest itself as wondering or poor return to center, not specifically death wobble. the trackbar/drag link angles mentioned above will result in bump steer, again, not specifically death wobble.

if everything new and tight, there are still 2 things i think worth checking... the steering box spacer, as mentioned above. also, the track bar bolt on the axle side. the mount is pretty thin sheet metal. even with the bolt being tight and the joint in good shape, the hole tends to wallow out, allowing slop. both this and the frame side steering gear mount can be quickly checked with a second set of hands moving the wheel, as described above.
in addition the the axle side track bar mount, check the frame side mount as well.

if there is any "wiggle" in any of these areas, death wobble could arise. at the same time... before i rebuilt and axle swapped my chitbox, i had all kinds of loose stuff, and it still went down the road fine. never wobbled. so maybe i am no help. :laugh2:
 
Thanks for the input everybody! Didn't make it back out the next day as originally planned.

-Had someone turn the wheel while I felt and looked for loose components. Still nothing seemed to have any play.

-Certain bumps used to give me a bit of bump steer. Felt like the back end would skip out on you a bit before the wobble started to happen. Haven't felt this lately, instead I get the wobbles at these bumps now. I've known the geometry is not ideal for a long time but it never got the wobbles so I just handled the bump steer. If you have ever crossed Eisenhower pass those slopes and bumps will give you a good white knuckled scare!

-The track bar is pretty beefy relative to the other parts. The bushing looks great and I can't flex it out of shape. The axle side hole is round. Before I had an adjustable track bar I had redrilled a new hole for the stocker. When I swapped out to the adjustable one, I filled the redilled hole and welded a little plate on the outside to reinforce the original. Still round. I tried turning all the frame side hardware but it was all tight. Couldn't wiggle the bracket at all. Johnny Joint on frame side of bracket feels tight to me. I don't have any other to compare with directly but I've had hiem joints on other vehicles and they'd be as tight as this johnny joint

-I'll have to measure the front pinion angle. It points pretty close to straight to the t case. When the wobble first started, I'd tried throwing the trans into neutral, t case to 4 high and other combinations to see if the front driveshaft had any influence on it. Didn't seem to make any difference.

-Track bar / drag link are not very parallel but never have been. I know this can cause issues but since it hadn't for ~15K I haven't tried this avenue

-New and old tires are the same size. 265/75/R16 ~32" on some aluminum rims. The tire shop didn't mention sand in the wheels when the new tires were mounted. Aluminum wheels usually crack rather than bend, they hold air and balanced up. At one point I did put an old wheel 31" i use for my spare. Same issues but one wheel was smaller than the rest.

-Steering box is tightly mounted and has a steel spacer between the box and frame. It also has a cheap brace connecting the output shaft to the passenger side frame rail. This is also tied in to 1/4" plate for my front bumper

-Alignment was checked after the dunes trip. The run up to test hill is rough and will beat components up!

Has anybody ever "box" in the upper arms with some 1/8" plate? I agree, they're flimsy. I've considered buy adjustable short arms but don't want to Just Empty Every Pocket. I'd rather spend the money on a long arm kit; I'd be really disappointed to spend a grand on the arms to still get the wobble. It is my ultimate plan to long arm it but I have another 9K to daily before I can retire her at 300K to the off road world

How does suspension travel change geometry? If the front axle moves up does it increase/decrease caster? What about when it droops? My caster is upper end of the specifications. When hitting the bumps, do they push the caster angle over the limit throwing the front end into its resonance? I could use the lower control arm adjuster boxes to pull some caster out
 
Living with bump steer. No clue why people do that.

The track bar is literally jerking the drag link every time suspension cycles even alittle this is wearing out the track bar and drag link joints.

No, death grip on the wheel isn't normal. Means driver confidence is low and fear has set, however great helicopter pilots where created from flying birds who shouldn't be in the air. They made it work and it made them better. Anyone can fly a healthy bird takes a real pilot to keep a ragged out tatterd war beaten bird in the air.


Fox the track bar and drag link geometry then worry about what's worn out.

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Upload pics so we can all see. 8 degrees of caster on 6 inches of lift with you stating the front pinion is pointed at the t case has me wondering if your caster is in the wrong direction... The to of the axle should be kicked back not forward... Sorry if this is a stupid suggestion as it is a little out there....

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Why wait another 9,000 miles to make it off road only? Replace it with a different daily driver now and Just Empty Every Pocket after Christmas.
 
Upload pics so we can all see. 8 degrees of caster on 6 inches of lift with you stating the front pinion is pointed at the t case has me wondering if your caster is in the wrong direction... The to of the axle should be kicked back not forward... Sorry if this is a stupid suggestion as it is a little out there....

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not stupid, i agree. caster is pretty high to have a perfect pinion angle without cutting and turning the Cs.
 
I swapped out the 3" coil spacer with the 2", adjusted the track bar, set the toe (~3/16" in) measured caster (D ~8, P ~9), pinion angle = 3 up. I took it for a spin and wobbled just like when I had the 3" spacer in. I then widened the toe up an entire spin to see how it would go. Eye balling it, tires appear to be pointed out. I hit the closes bump to home without shake. Turned around hit it going faster with another success. I was going to cruise around this afternoon hitting bumps seeing how it does.

I took some pictures of the angle finder the best I could before swapping to the smaller spacers. I'll get some of this current alignment if it works out
 
All resolved, alignment?

Last time I had the wheels off of Stripy Jeep, doing drop brackets, I got 6’ of thin aluminum angle. Cut it in half, drilled a hole for a lug stud in the middle, and bolted it to the hub. For like $15 and and extra five minutes work, I have good references to measure for toe without a helper or trying to “catch the same lug on the front and back of the tire”.
 
I took a hiatus from the garage over winter. I couldn't get myself to go out there if I didn't have to. Too cold..

2000 miles later she has stayed wobble free. I left it on the 2" coil spacer 3" spring up front. Rear was lowered on an adjustable shackle to level out with the front. Its been driven this way over the past 2k.

I cut up some 36" sections of angle iron to help measure the toe angle just to be sure. Toe angle was about 1/16" OUT. Tires haven't worn unusually. I closed up the toe to be square and haven't had any problems yet (~100 miles)

Thanks for all the help!

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