death wobble
the death wobble is caused by having all 4 coil springs. I only know this from the Jeep Grand Cherokee that I owned before discovering Rovers. Here is a very long list to look for sorry it is about jeeps but it is what i know more about. I haven't experienced this with my Rovers. I hope it helps. With my Jeep the problem was the track bar front and rear had to be adjusted and I put New front and Rear stablizers on.
As you have already found out, Death Wobble, the horrible front end vibration that starts when one wheel (usually the right) hits a bump around 40~50mph, is the worst possible downside to having a coil-sprung vehicle with a track bar setup such as the WJ, XJ, ZJ, and TJ use. Death Wobble is also extremely difficult to try to diagnose, because it is actually caused by slop in the entire steering system as a whole, not by one component. To diagnose correctly, one needs to look for "play" everywhere there is something that could have "play" in it. It's time consuming, and downright dangerous while you are in "test phase", trying to exorcise this demon from your Jeep.
The thing I tell people to start with is a visual inspection. Spend 10 minutes under the front end and visually inspect each one of the steering components for shiny steel, which would be indicative of metal that's moving around when it's not supposed to be. Pay careful attention to the track bar, as it's usually the culprit in most cases. If any of your bolts are even the least bit loose, Death Wobble can manifest itself and make your life a living hell.
If everything looks to be "normal" and you've checked bolt tightness on the track bar, the next thing to do is to start with an alignment, making sure that caster is set correctly as well as toe-in. If you have been offroading and have bent your tie rod even slightly, it'll throw off the alignment. Plus, it's only $40 or so.
If you are certain that it's set correctly and you've not replaced any other front end components recently that may have caused the oscillation to begin, I tell people the next most suspect thing is the factory front track bar. Over time, the tie rod end on the upper portion of the bar develops "play" in it, and the lower end has a rubber isolator bushing in it that allows the oscillation to occur. Aftermarket bars generally come with urethane bushings that allow much less "play" in the way of movement than the factory rubber bushings do. The problem with most aftermarket track bars for the Jeep is that they also come with either a heim joint, Johnny joint, or tie rod end on the upper end of the bar, which works fine for a while, but wears out over time, leaving you right back where you started, with a mess in your shorts, a temporarily deaf right ear from the wife screaming, and the frustration with your entire Jeep in general...NOT good. The reason why I created my Track Bar Conversion for XJs and ZJs is to eliminate that problematic (and expensive to have to replace when it wears out) joint as well as for the additional flex benefits. If you are running an XJ or ZJ with more than 3" of lift, I highly recommend you check it out. Another product we have found to work VERY well in getting rid of Death Wobble is our exclusive SuperDurometer Track Bar Bushings, which are also available for the Track Bar Conversion. They are about twice as hard as the typical polyurethane bushings that come in most aftermarket track bars, which are typically made by Daystar or Energy Suspension. They are also one of the least expensive replacement parts in the steering components, so they make sense to try first. Many aftermarket track bars as well as the stock track bar are completely ineffective in managing Death Wobble due to their "effective angle of operation" if you are above 3" of lift. Bear in mind that another alignment is necessary after replacing any front end components if Death Wobble still remains. Sometimes you get lucky and don't need one...but be wary.
The next thing to check is your steering stabilizer. I recommend replacing the stabilizer along with whatever worn components that you find under the front end, as the combination-punch is typically more effective than the parts alone, since DW shakes EVERYTHING, and loosens up other components at the same time. I've found that replacing the stabilizer alone often times doesn't eliminate death wobble directly, but that it usually helps with some additional poor handling characteristics that cause the onset of Death Wobble, such as wandering, and a new one seems to tighten up the entire steering system. I ONLY recommend the OME SD40 stabilizer because it seems to be tighter than the other models on the market. It's also the most heavy duty. This stabilizer is something that I recommend to everyone who is having trouble with DW because it's one of the least expensive parts to replace.
Here are some other components to check over for looseness or improper movement:
Tie Rod Ends, ball joints, Track bar mounting bracket bolts, steering box bolts, and track bar ends. Another product that we've made due to a need, is our ZJ Steering Box Brace, which holds the steering gear box tightly, allowing the additional stresses of running larger-than-stock tires be directed to the frame rails, rather than to the three little bolts that hold the gear to the frame, which get loose and if they do, will snap and leave you stranded. I don't currently make one for the 6cyl ZJ, but if you have an XJ, you can find one at
www.barnettperformance.com.
The last thing that I can mention that has caused Death Wobble in the past is hub bearings. If there is a little slop in them over the years and miles, they MAY indeed help to cause the oscillation as well. I mentioned them last because they are the most expensive to replace and least likely to be the root of the problem. While you have the front end apart, you should consider adding some offset upper ball joints to your Jeep to return the caster back to what a stock Jeep would be if you are running say 4" of lift or more. I don't necessarily recommend this for the '93~'95 full-time 4x4 (NP249 transfer case) ZJ models, though, because it tends to add more vibration to the front drive shaft since you are also turning your pinion angle downward in conjunction with the caster angle improvement...you can't have one without the other.
In the end I would take it back and say hey I didn't have this problem untill you touched it.
