There are few things more terrifying than experiencing "death wobble" in your Jeep for the very first time. More times than not, it'll happen out of the blue soon after hitting a bump in the road or a pot hole, driving over a rough set of rail road tracks or even after driving over rhythmic sections of expansion joints in a concrete laid highway. The sensation is unbelievably violent and so much so that it can feels as if your whole Jeep is about to tear itself apart. You literally feel as if you're about to die and the only way to get it to stop is to bring your Jeep to a stop. Unfortunately, some people become so traumatized by death wobble that they become reluctant to drive their Jeep again and others go so far as to sell it.
What is Death Wobble?
Death wobble is a violent, uncontrollable shaking of your entire Jeep caused by extreme oscillation of your front axle. This is NOT to be confused with a vibration or even a "really bad shimmy" in the steering wheel. The later would be a common problem associated with tires that are out of balance. If you're not sure if you have death wobble, I can almost guarantee you don't. Experience it once and you'll know for sure.
Common Causes of Death Wobble?
FRONT TRACK BAR:
Death wobble is a condition that can occur when you have loose or worn out suspension and/or steering components. The most common cause of death wobble is a loose front track bar bolt, worn out track bar bushing, a failing track bar mount and sometimes even a track bar that is physically bending or flexing. If you've just come off the trail and now have death wobble, there is a good chance your front track bar bolt has worked itself loose and re-tightening these bolts to 125 ft. lbs. may be all you need to do to fix it.
The second most common cause of death wobble are worn out ball joints. Unfortunately, the factory ball joints contain components made of plastic wear out quickly especially if you're running much larger tires on wheels with a lot less back spacing. Also, these components are susceptable to heat and can melt if you fail to remove them prior to having C-Gussets welded onto your front axles end forging.
For the most part, the only things that I have found to allow death wobble to occur are problems associated with a front track bar and/or ball joints. Other loose, worn out or damaged suspension and steering components can allow it to occur as well but, they aren't as common. Now, there are a host of things that can help instigate or trigger death wobble and the most common of these are tires that are out of balance. The rythmic shimmying of unbalanced tires will put a strain on suspension and steering components and can easily work bolts loose. Left unchecked, this additional movement will eventually compound and be exaggerated until it results in death wobble. Other things I have seen that can instigate death wobble include a toe-in setting that was drastically off, a caster setting that was significantly less than the factory +4.2 and I have even seen where one front shock that wasn't valving properly trigger death wobble as well. But again, most of these things cause the wearing out of components and/or the loosening of bolts and once that occurs to something like your front track bar, death wobble can ensue.
Common Myths About Death Wobble
STEERING STABILIZER - The most common myth about death wobble is that it can be caused by a damaged, worn out or missing steering stabilzer or that it can be "fixed" by installing a new heavy duty unit. Assuming your suspension and steering components are in good shape, installed properly, dialed in and tightened to the correct torque setting, a steering stabilizer shouldn't even be needed to operate your Jeep safely. Yes, having one is nice but, it's far from something you "need". Will a steering stabilizer help prevent death wobble from occuring? Yes, it can "help" but, at best, all it'll do is hide or mask the real cause of your problem.
TOE-OUT - While a Jeep does have 4 wheel drive capabilities, it is for the most part considered, a rear wheel drive vehicle. Because of it, the front wheels are designed to have a toe that is set inward ever so slightly. As you move forward, your front tires will get pushed outward, will be more parallel and, in addition to providing improved tracking, it will help ensure better tire wear as well. While setting your toe outward can help prevent death wobble (it's actually something I would even recommend as a bandaid to get you home), it WILL NOT be a "fix" for whatever is causing your death wobble. Like a steering stabilizer, setting your toe out will only serve to mask the real problem at hand.
Steps You Can Take to Fix Death Wobble
Before I start, I need to state for the record that I am not an expert on suspension nor would I pretend to be. Any advice I can offer is solely based on my experience working on our JK's, wheeling them and driving them everywhere both on and off pavement. Unlike some, we do not trailer any of our Jeeps and since 2007, have racked up well over 110,000 miles on our White 4-door JK, over 50,000 miles on our 2009 Sunburst Orange 4-door JK before selling it, over 15,000 miles on our 2007 Silver 2-door JK and have even put on close to 20,000 miles on our new 2012 Dozer 4-door JK. To date, we've had the unpleasant pleasure of having death wobble on all but our 2012 JK. However, I am happy to say that we have been able to successfully fix it on all of them. Having said all that, the below information are steps that I've been able to take to find and fix every instance of death wobble that we've had. With any luck, they'll be able to help you too.
1. GET YOUR TIRE BALANCED:
Getting big off road tires balanced is hard to do and it's not uncommon to need 2-3 visits to get them on right. Even if you've had them balanced recently, I would still recommend that you do it again before proceeding. While unbalanced tires will not "cause" death wobble, they can instagate it and, if they are still off, it will make it harder to identify the actual source.
2. SET YOUR CASTER:
You ever get a shopping cart at the grocery store with a bum wheel? You know, the kind that wobbles all over the place even though you're going straight. This occurs because for whatever reason, the wheel in question has very little to no positive caster on it. Likewise, a Jeep with little to no possitive caster can instigate death wobble as well. Lifting a Jeep will effect your caster and it is important that you have it set as close to the factory +4.2° as possible. Having more is better but, that can cause driveline vibrations and that's not something you'd want to have.
3. REMOVE YOUR STEERING STABLIZER:
Because a steering stablizer will dampen movement in your front axle, leaving one in place will make it difficult to locate the actual source of your death wobble. Removing it will cause your death wobble to occur more consistantly and more predictably and that'll not only help you to find the source of your problem, it'll help you to know it's actually fixed.
4. CHECK YOUR FRONT TRACK BAR:
Wheeling is hard on your suspension and steering components and having a bolt come loose on your front track bar is very common. More times than not, re-tightening your track bar bolts to 125-130 ft. lbs. of torque is all that is needed to fix death wobble. If your bolts check out, carefully examine the bushings and mounts for signs of cracking, tearing or fatigue on both the axle and frame especially if you have a relocation bracket that is not reinforced installed. The added height of a relocation bracket can act as a lever and over time, can cause your weak factory mounts to fail through metallurgy. Some will suggest that you also check the mounts for any signs of wallowing of the bolt holes and if they are, they would recommend that you have a plate or washer welded on to tighten things up or, install a new larger diameter bolt to help make up the difference. However, torque is what is important and ultimately what holds everything together like a vice - NOT bolt size. You can read all about replacing factory bolts with grade 8 shouldered bolts here: Jeep JK Wrangler Grade 8 Replacement Bolts - Do I Really Need Them?
Last but not least, check your track bar to see if there's any flexing in it. This is something I have seen with JKS track bars and a few other aftermarket units and you can see it happening just by having someone turn your steering wheel back and forth while you give it a look.
5. CHECK YOUR BALL JOINTS:
There are two different types of movements you will see in your ball joints, the first is called RADIAL (shifting side to side) and the other is AXIAL (up and down). The amount of radial movement you see should not exceed 0.060" (1.5mm) and axial movement should not exceed 0.050" (1.25mm). Because it doesn't take a whole lot to be off, the best way to measure ball joint play is with a dial indicator. Here are steps you can use to check them:
1. From the axle, use a good floor jack to lift one of your tire off the ground. If you don't have a good floor jack, set your axle on a jack stand to hold it up securely in place.
2. From the side, place a long pry bar under the tire and have someone lift it up and down while you watch the lower ball joint for axial (up and down) movement. Any movement more than 0.050" is too much and would indicate that your ball joint is bad. Of course, if you can see this movement with your eyes, it's definitely bad.
3. Next, grab the tire at the 12 and 6 o'clock position and try to rock it back and forth while you have someone watch the upper joint for any movement. Any radial (side-to-side) movement more than 0.060" is too much. Again, if you can see the movement with your eyes and without any dial indicator, it's probably bad as well.
If they check out, I would check your unit bearings as well.
6. RE-TIGHTEN YOUR BOLTS:
Death wobble is so violent that it can and often does work bolts loose with each episode you experience. In other words, if you have an episode occur while going through this checklist, take some time to re-torque everything again. Yes, it's a pain, but in the long run, it'll help you to find and fix the actual cause of your death wobble a lot faster.
Useful Links & Diagrams
Torque specs on every bolt your Jeep JK Wrangler has can be found on this link:
Jeep JK Wrangler Torque Spec Sheet
The diagram below will help you to identify all of your front end suspension and steering components.
Again, the information and steps outlined above are just what I've used in the past to find and fix every instance of death wobble that we've had on our JK's. With any luck, they'll be able to help you out as well. If you have any questions, please feel free to post them up here.