The culture surrounding off-road vehicles, as with pretty much anything motorized, is filled with grand tales of harrowing bravado. One subject that always seems to come up during story time in our shop is that of the repugnant death wobble, especially when a Jeep product is involved. But what is death wobble and how can it be remedied?
The story usually goes along the lines of the vehicle owner tooling along at a reasonable rate of speed on an otherwise lovely day when the car hits a bump and, for no apparent reason, begins to shake violently from the front end. The terror-stricken driver will go on to describe how it took every shred of skill and wit to avoid side-swiping a church van full of nuns and disabled persons riding in the adjacent lane while keeping the vehicle from rolling over. It typically concludes with the truck coming to a screeching stop, mere inches from a young boy scout who was helping an elderly citizen and a cute little puppy across the road. A less dramatized account is illustrated in this video.
The phenomenon of death wobble tends to occur in vehicles with coil-sprung front axles, although highly modified and/or worn rigs with leaf springs are not immune to it. While a coil setup is common in Jeeps, it is also found in 4WD Dodge pickups, later Ford Super Dutys, and older Land Rover models, bearing in mind that Land Rovers rarely stay running long enough to wear out steering components. The physics of death wobble involve a perfect storm of worn steering and suspension components oscillating violently when introduced to a lateral (from the side) force. Adding altered suspension geometry into the mix (like from a lift kit) only amplifies these effects.
The tricky part about dealing with death wobble is that it typically is caused by multiple conditions. If the vehicle is lifted, the dealer will likely laugh at you and tell you to go away. If it’s not lifted, they’ll likely blame it on wheel balance to avoid litigation from lemon law lawyers. In reality, you’ll need to go over every possible wear part in the front end. Every bushing, ball joint, and drag link must be carefully inspected. Awkward tire balance can even play a factor, although it is usually just the catalyst that sets the death wobble in action. In some rare cases, I’ve even seen bolt holes that have worn too large and added to the death wobble effect. Even the steering gear needs to be gone over because, as in the video, they do eventually become sloppy.
Once every suspect component has been sorted, it’s time to look at the alignment. Something to really pay attention to is the caster, since it affects how road forces feed back into the steering. On a stock vehicle, this shouldn’t be all that far off but when you lift a solid axle, you better believe that caster will change. Speaking of lift kits, this why adding adjustable control arms and track bars are critical since their job is to position the axle under the vehicle. Once lifted, the adjustability allows the steering and suspension angles to be brought back into spec.
Remember that addling lifts and big tires will put added stress on the front suspension components so make sure that everything is in good form before bolting up those Super Swampers. While you’re under there, if anything looks questionable at all, replace it and try and find a heavy-duty version while you’re at it. Don’t be that person who wipes out a church van.