Still experiencing death wobble [Solved!]

nk24

nk24

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Last weekend I experienced extreme death wobble in my new to me LJ at 75 mph on the interstate. I had driven about 500 miles on and off road prior to this with no issues. This is my third TJ and I had never experienced DW before. It’s downright frightening at 75 mph.

I started looking for the problem by checking torques on the entire suspension. Upper and lower control arms were all good, along with the frame side track bar bolt. The axle side track bar bolt was not at spec so I tried to tighten it. After a several small cranks with the torque wrench the bolt snapped into two pieces.

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Could this bolt being slightly under torque spec be the root issue of the DW? The bracket hole does not look to be wallowed out so I lucked out there.

I’ve ordered the Black Magic Brakes HD replacement kit but I’m not sure I can really do anything else until that arrives. Looking back I should have done a dry steering test first before torquing everything. Once I’ve got the track bar back in I’ll get the tires rotated and balanced as it has been a while since they were balanced.

While the track bar is out, should I consider rebuilding it? It is a Currie that was installed 10 years and about 45,000 miles ago.

I’m crossing my fingers that the issue is as simple as this. I’ve got a trip planned in April and obviously need to get this sorted out prior to that.
 
Yes, a loose bolt can cause this. It could also be a bad bushing. I would replace the 10 year old bushing, reinstall, and do the dry steering test again.
 
That loose bolt will certainly make it much easier for DW to develop but something else has to actually trigger it. An out of balance tire, bump on the road, etc.
 
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What @Jerry Bransford said. I developed a DW about this time last year. Hit a chuck hole and away we went. Root cause was a loose track bar bolt and slightly egged out hole.
 
Jerry Bransford said:
That loose bolt will certainly make it much easier for DW to develop but something else has to actually trigger it. An out of balance tire, bump on the road, etc.
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It was definitely triggered by bumps in the road. The first time was at a bridge abutment. Subsequent events were triggered by chunked pavement.

I’ll get the tires rebalanced as soon as I get the BMB kit installed.
 
mushdogs said:
What @Jerry Bransford said. I developed a DW about this time last year. Hit a chuck hole and away we went. Root cause was a loose track bar bolt and slightly egged out hole.
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What should the diameter of the axle side hole be? Or maybe a better question is how close should the bolt diameter be to the hole diameter? The bolt that snapped is quite a bit smaller than the hole.
 
nk24 said:
What should the diameter of the axle side hole be? Or maybe a better question is how close should the bolt diameter be to the hole diameter? The bolt that snapped is quite a bit smaller than the hole.
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I couldn’t tell you the exact diameter. It didn’t take much to ream it back round, both it and the bushing sleeve. What caused the egging was the bolt was just slightly smaller than the bracket and sleeve. Likely put there when the lift was done by the PO. The bolt that replaced it was a close fit, but I don’t recall the size.

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Jerry Bransford said:
It's a 10mm, this is what I'd replace it with.... https://www.shop.blackmagicbrakes.c...high-strength-SS-Bolt-HD-FLAG-NUT-SS-BOLT.htm

Don't worry about the hole diameter, just torque to spec and you'll be fine. Spec tightness is 40 ft-lbs. and much over that with the factory bolt will snap it. You can run roughly 50 ft-lbs. with the ARB SS bolt from Black Magic IIRC IIRC. Can you please refresh my memory on that @mrblaine?
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Thanks Jerry. I ordered that piece earlier.

I’ve seen different values for the stock torque spec, 40 and 55 ft-lbs. Also the Currie instructions say 75 ft-lbs. I’ll be curious to see what @mrblaine says about the BMB kit.
 
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nk24 said:
Thanks Jerry. I ordered that piece earlier.

I’ve seen different values for the stock torque spec, 40 and 55 ft-lbs. Also the Currie instructions say 75 ft-lbs. I’ll be curious to see what @mrblaine says about the BMB kit.
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Same here on all that. Blaine gave me his recommendation on that bolt when I bought it from him but damned if I can remember what it was. It was a little lower than I expected to hear but that's what I went with.
 
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nk24 said:
Thanks Jerry. I ordered that piece earlier.

I’ve seen different values for the stock torque spec, 40 and 55 ft-lbs. Also the Currie instructions say 75 ft-lbs. I’ll be curious to see what @mrblaine says about the BMB kit.
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60 works fine. 75 is the same as the knuckle bolts that hold the unit bearing in. No way the stock track bar bolt will handle that.
 
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As said earlier, BMB bolt and flag nut kit is on the way.

Looking to rebuild the track bar. I think these are the two parts I need:

Axle side

Frame side

I've never had a component with Johnny joints until now. I see they sell a Johnny joint tool. Do I need this as well? What does it do?
 
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nk24 said:
What should the diameter of the axle side hole be? Or maybe a better question is how close should the bolt diameter be to the hole diameter? The bolt that snapped is quite a bit smaller than the hole.
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The bolt squeezes the bracket, the bracket squeezes the bushing sleeve, and holds it in place. None of the holes care what size the bolt is.
 
After installing the BMB bolt kit, I did a dry steering test. Nothing stood out to me but hopefully one of you eagle-eyed experts can see something.



 
i don't catch any odd movements .........looks like it could use some grease though.
 
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A short while back I started experiencing really bad death wobble. I did a number of things to fix it. Replaced the track bar bushing, balanced the tires, did an alignment, replaced the tires, replaced tie rod ends. The death wobble went away but still it seemed to be right on the edge of death wobble when I hit bumps. Then I discovered the steering damper was loose on the frame end. I tightened that up and all of that sensation of imminent death wobble went away. So while we know that replacing a steering damper is seldom a cure for death wobble, just make sure it is tight.
 
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TurboTJ said:
So while we know that replacing a steering damper is seldom a cure for death wobble, just make sure it is tight.
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Replacing or tightening a steering damper is not seldom the cure, it is NEVER the cure for DW. All it can do is help to mask the symptoms. Like covering a melanoma skin cancer with a band-aid.
 
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