Front suspension issue

[madmax]

So I am going down the road at 50 mph in my 88 Sporttruck Comanche when I hit a bump in the road. The steering wheel begins to shake and continues to shake until I come to a full stop. Visually, I could not see any problems. I continued driving slowly home (45 mph max) and no further problem. What could cause this reaction?? Also, If I were to rebuild the front suspension, what exactly should be replaced or repaired? The truck is in nice shape with only 84,000 miles. Just need to figure out how much need to be done and what the cost could be for a full rebuild. Thanks for any help!

[Lee21490]

Check your track bar. Its usually the culprit.

 

[gogmorgo]

Sounds like the Death Wobble. Relatively common Jeep issue, or really anything with a solid front axle. Basically a vibration gets transmitted to the other side and they go into harmonic resonance. Often triggered by a bump, could be caused by worn components, poor tire balance, bad suspension geometry, a change in the weather, a rise in gas prices, low blinker fluid, depends on who you ask.

Do you have a lift? If so what all has been changed from stock?

[Eagle]

TIRE BALANCE!

[madmax]

Lee21490--Does the photograph also apply to a 2WD Comanche? Thanks for the help!

[Doc.]

2wd is the same.

Check everything, also check steering stabilizer for leaks, age. If it's shot it can't do it's job. Even look at the shocks, just because.

[madmax]

Gogmorgo--it's a bone stock 2wd Comanche. I think the shocks actually may be original as the truck was stored for many years before I acquired it.

[mikekaz1]

that's a really good informative picture!

[gogmorgo]

2wd suspension is identical to 4x4, as was said, just with a solid beam instead of an axle. The issue that happens with lifted jeeps is that the track bar and drag link don't end up parallel, which means that things are constantly binding, flexing, and releasing. Any worn bushings, ball joints (especially at the tie rods or track bar) or bent components could cause something similar.
Then there's the matter of the vibration that goes into harmonic resonance, which could very well be caused by a simple tire balance issue.
The steering damper is a solution to reduce the vibrations, and/or prevent them from going into harmonic resonance, although some view it as a bandaid solution and leave it off. As such it's actually missing from the above photo present and accounted for it the photo, unlabelled and hiding behind the drag link. It mounts between the eye in the middle if the drag link (right below the adjustment) and the frame passenger end of the axle. Not all vehicles originally shipped with one, I don't think, but I can't confirm that.

I should add as a disclaimer that I have never fought this issue myself. My limited knowledge comes from stuff I've read on the internet and a basic understanding of suspension geometry. And like all things on the internet, there's pretty serious debate about it every time it comes up, and very little consensus on a specific individual cause for the problem.

But I'd start by rotating the rear tires forward to check for tire balance problems, then start investigating the components themselves.

[madmax]

Gogmogo:  Thanks very much. I also noticed that the steering damper,  which I have on my MJ, was missing in the photo. My plan is to check for balance and also check the condition of all the bushings, tre's, and ball joints, and replace the front shocks, which are quite old.

[Doc.]

Look closer, it's not missing in the photo just "hiding" behind the drag link and not labeled but it's there.

Yes much debate over the dampener. Some people like to say it's a band aid to some other problem. Yes, it could be, but at the same time why did the factory put it on there then. Because it's needed. I have had some experience with death wobble on a couple different rigs. The one issue was tires. They balanced fine, looked good, and a friend of mine put them on his Ford Ranger without issue. But with a new set off tires my issue was gone. The other one that comes to mind was the bolt on a newly installed track bar came loose. I know there was other cases too but danged if I can remember them. I'm thinking I've seen a bad wheel bearing caused it too. As said, check everything, there is no one common cause for the issue. It could even be the nut behind the wheel! Very rare though.

[gogmorgo]

Right. So it is still there. It connects from the drag link to the front axle at the passenger side, not to the frame. Not sure what I was thinking there, looking for it in the wrong spot. I'll fix my post above.

 

I'm not sure why people think it's just a band-aid either. Dampers are legitimate engineering solutions for preventing and reducing vibrations and/or oscillations, and in some cases critical for preventing resonance.

[mikekaz1]

I get it every once and a while in my TJ if I go around a bend at 55-65mph. other then that its fine.  and that's with all brand new steering and arms

[Gene]

Hi everyone,

 

I went through this a while ago with our 88 Comanche. At about 45 mph or higher, when hitting a bump on the road, the steering wheel, front end, and entire truck would shake violently. All I could do was stay off the gas and brake and wait until the speed dropped to below 30 mph.

 

Front end was tight. Alignment was good. I had factory alloy wheels, and had them rebalanced with stick on weights, which helped a little. Replaced the steering damper with a heavier model, which helped a little. But there was still a significant "death wobble".

 

Problem was not solved until I got a set of junkyard steel wheels, used the same tires on the steel wheels, and had them balanced with real weights. Haven't had a problem since.

 

Gene