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Death Wobble Questions (I searched first)

trailturd

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86 MJ 2.5 AX5 converted to 4wd with HP30 from a 96 xj. Added a Rusty's 3" lift when I did the conversion. Has had bad death wobble ever since. Replaced trackbar with a new stock length, since there was some play in the old one. Seemed to make it worse. Aligned with 6 degree caster, not sure if that is enough, considering getting adjustable lower control arms to get the caster in the 7-8* range. As well as eliminate the question of worn out LCA bushings. Running out of things to check and don't want to just throw money at it without having an idea of what's causing it. I got underneath it and had someone cycle the steering, tie rod ends all seemed fine. Steering box is tight to the frame, I swapped that out when I did the 4wd conversion as the stock box was non power steering. Front drive shaft has new u-joints also done during the 4wd swap. Ball joints and wheel bearings all checked out fine. Track bar moves a very small amount at the axle, but it looks and feels like it's just the bushing flexing slightly. What am I missing? I can drive 40-50 down a washboard rough gravel road and it's fine. Get on smooth pavement and hit an expansion joint wrong and all hell breaks loose. Any ideas? I'm at my wits end and about to light this thing on fire
 
If you can feel flex/wobble in any joint then you need to consider replacing it. Especially any wobble at either end of the track bar.

If the new track bar seemed to make it worse you may have a bad part. Do not assume that new parts are good parts.

One thing I do not see mentioned in your list is tire balancing. That can be a cause too.
 
If you can feel flex/wobble in any joint then you need to consider replacing it. Especially any wobble at either end of the track bar.

If the new track bar seemed to make it worse you may have a bad part. Do not assume that new parts are good parts.

One thing I do not see mentioned in your list is tire balancing. That can be a cause too.

The rubber bushing at the axle end of the track bar does compress slightly when turning the steering wheel. You can't see it, but I can feel it with my hand on the joint. Not sure how much deflection is allowable, but as stated it is new. The tires and wheels are stock take-offs from a 2016 rubicon so I'm assuming they are still factory balanced. Just to eliminate that I'll rotate them tonight and see if that makes any difference.
 
As stated, new cannot be assumed good. There are plenty of defective, new parts to be found out there.

2016 take-offs still need to be verified. How many miles before being taken off, and how stored? 2016 take-offs also mean adapters. Those should be checked too.
 
At 3" I'd get a good adjustable track bar to get the axle centered vs a stock one. What was included in your 3" lift, just springs?

Other spots to look at on DW if you haven't already:

1. Steering box spacer. Its aluminum and likes to disintegrate. If its gone the box can flop around since its not tight to the frame rail.

2. Axle end UCA bushings.

#1 was the solution for me when I had similar symptoms to yours. Jeep drove fine but there was one expansion joint that always made it wobble.
 
For what its worth, I have two identical XJ's. After installing 3.5" lifts, one had death wobble and the other didn't. There seems to be a razors edge difference between death wobble and no death wobble. My lift kits came with adjustable lower control arms. Tweaking the caster helped, but thats a balancing act between good caster angle and bad pinion angle (a whole other subject). The stock tie rod is a bit flimsy, so i replaced it with a heavier one made from 1/8" wall DOM and that fixed the problem.
 
At 3" I'd get a good adjustable track bar to get the axle centered vs a stock one. What was included in your 3" lift, just springs?

Other spots to look at on DW if you haven't already:

1. Steering box spacer. Its aluminum and likes to disintegrate. If its gone the box can flop around since its not tight to the frame rail.

2. Axle end UCA bushings.

#1 was the solution for me when I had similar symptoms to yours. Jeep drove fine but there was one expansion joint that always made it wobble.

Steering box was just replaced and the spacer was fine. I converted to power steering when I did the 4wd swap
 
As stated, new cannot be assumed good. There are plenty of defective, new parts to be found out there.

2016 take-offs still need to be verified. How many miles before being taken off, and how stored? 2016 take-offs also mean adapters. Those should be checked too.

So how much bushing deflection is acceptable before being deemed defective? Only way to have zero movement there would be a heim joint. Adapters were checked yesterday, should’ve rotated the tires then.
 
I replied at the Comanche forum. I'd upgrade the trackbar. Get a fixed lower control arm for a 3"-3.5" lift. Possibly use a WJ lower control arm and a Core upper control arm. Check ball joints, and possibly replace them. I use XFR on one build, Alloy USA uppers and Mevotech TT lowers on another. The Teraflex ones look good. Also, what was causing my DW, was a cracked frame, by the steering box. I would upgrade the stock steering box brace to a steel one. I think $35-$50.
Also, mine started right after an alignment. ??? Also, need to reinspect any and all parts after DW. It can and will damage parts. I think the worn bushing in a Set of JKS lower control arms were due to this. Also, the upper Rough Country control arms were damaged too. I replaced the Rough Country ones with the JKS ones.
 
So how much bushing deflection is acceptable before being deemed defective? Only way to have zero movement there would be a heim joint. Adapters were checked yesterday, should’ve rotated the tires then.

By hand: None.

The factory design with a ball joint on the frame side is a bad design. Far better to convert to a double shear mount. Core 4x4 makes a good one for a reasonable price.

On the axle side, often the hole has been wallowed out. Kevin's Offroad makes super hard bushings and also offers a bolt upgrade that takes the bolt size to 9/16". Their bolt upgrade includes a flag nut.
 
Just wanted to give everyone a update. I replaced the track bar with a double shear adjustable one and centered the axle. I replaced the stock lca with adjustable ones with rubber bushings and set them at 16.09”, replaced the steering stabilizer, and I noticed the motor mounts were trashed so replaced those too. Jeep drives great now, just wish I would’ve done all of that right from the start.*
 
Awesome.

Thank you for the update and letting us know what you did.

BTW, if you only did motor mounts, give some thought to the trans mount too. Mine looked just fine when I did motor mounts (which did not look fine), but I decided to do it all while I was at it. Turned out looks don't necessarily equate to reality with the trans mount. Mine was in poor shape, in spite of having a good appearance. Once removed from the vehicle it pretty much fell apart. Gravity was holding it together.
 
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