Death Wobble
So you are traveling along in your Jeep and hit that "just right" pothole or rail road track and your whole front end starts to shimmy so bad you think you are going to run off the road. It's the dreaded "Death Wobble!" Some say a good steering dampener will fix the problem. Well, it might mask the problem, but it certainly doesn't fix it. Just in case you didn't know, a steering dampener is like a horizontal shock absorber that has friction on both the compression and extension stoke. It's attached to the steering rod and something solid. Then it dampens any tendency for the system to make fast moves, just like a shock absorber does in your suspension system.
First, don't confuse Death Wobble with a vibration you feel from a tire that is out of balance or the tread is coming loose. You feel that mostly in your seat and your feet. Death Wobble is a violent back and forth shaking of the steering system while under way and is the result of something loose in your steering system. You feel that mostly in the steering wheel. Loose connection points can be on your tie rods, track rods (or panhard rods), steering box attachments, track rod brackets and steering arms. Anything that has to do with keeping your vehicle going where you are trying to point it. I've seen it caused by a tiny crack in a track rod bracket and another time in a cracked cross-bracket stabilizing the left and the right side of a CJ's frame. I've seen it when a steering box brace cracks, worn tie rod ends and recently a worn heim joint being used as an adjustable track rod end. Here is a photo of that end I recently removed from my 2007 Jeep JK. You can see some fabric that has oozed out of 
this aftermarket joint. It was on the end of an adjustable track rod I received when installing an aftermarket suspension lift. No, I don't know why the heck they used fabric here in a joint subject to such tremendous force but they did! It could have been bullet-proof Kevlar, but it sucked as a friction medium in this use.
I wasn't able to see this fabric when I looked at the installed joint because bushings, bolts and braketry was in the way. I also wasn't able to see it move when I had someone turn the steering wheel back while I laid under the vehicle inspecting everything. However I found it by grasping it with my hand while my assistant turned the wheel back and forth enough to put a strain on things. I could just feel it moving in my hand.
Once I replaced this one with the original end, the Death Wobble and all other wobble went away.
So how did I discover I had this malady in the first place? By taking the steering dampener off and driving the Jeep. Right away I could feel a wobble that the dampener had been controlling or masking. Then, when I went across some rough spots in the road, the Death Wobble hit and I had to nearly come to a stop to get it to quit.
Then is was back to the shop and, leaving all the wheels on the ground for added resistance, have my lovely wife turn the wheel back and forth (with the engine running) about 1/2 a turn each way to find the culprit by feeling each joint to see if it was tight or not. When I removed the track rod, I could barely move this joint and could see the fabric they used coming out of it. By the way, this came on a track rod sent by a very well-known after-market suspension company who is known for quality products. However, in my opinion, no heim-joint has a place in steering components on vehicles that are going to be used on and off-road. Maybe on sprint cars and vehicles used for short-duration racing but never on vehicles that you expect to put thousands of hard miles on. They just don't live long. Just my opinion after trying several of them over the years, mind you.
Since I had established the ideal length of the adjustable after-market track rod by adjusting the joint during installation, I placed the after-market rod on the concrete, traced around it and marked the exact location of the centers of the ends. Then I whacked off the end with the heim on it with my chop saw. 
I then measured carefully and whacked the same end off the factory track rod so, when I welded that end back on to the after-market track rod, it was the exact same length as it was with the crappy heim joint on there. The other end of the track rod actually had a good, non-adjustable joint on it so no problems there. The aftermarket track rod was longer, so I had to use it instead of the original with my suspension lift. Besides it was larger in diameter and, hopefully, stronger.
After putting everything back together, I drove it without the steering dampener and no more wobble. Everything felt very solid and the steering wheel was still almost centered, so I must have gotten the measurements pretty close. If I had missed much on matching the length, the steering wheel would have been way off center and the JK's sensor system would have squawked about it. I did have to slightly re-center the wheel with the tie rod adjustment but everything still handled right so no worries.
Once I knew nothing else was loose, I re-installed the steering dampener using the excellent Woods steering dampener relocation kit which gets it up out of harm's way.
Much has been said about the need for steering dampeners. Some other writers and I agree that they can and do mask problems in the steering systems and seldom should be used to "fix" serious wobbling. Even if they do work for that. The root cause of wobbling is most often even a tiny bit of slop somewhere. Without a dampener, the system then oscillates within this slop, bouncing off each end of its excursion giving you a terrible case of the wobbles. This could be the precursor to ever larger problems in the future. it really doesn't take very much slop to give you a severe case of the Death Wobble.
If you have a lifted rig with big tires and have even a little mechanical skills, I recommend taking off the dampener once in a while and carefully driving your rig on a rough road. If you feel noticeably more wobble than you did with it on, go find it and fix it before something breaks off your rig and sends you into a ditch or someone else's vehicle. Then, once it's all fixed, reinstall the damper just because. Or not, your choice. Having one on there is definitely safer than having Death Wobble and might slow down rapid deterioration once slop occurs.
Jim Piatt