Death wobble. No other pair of words strikes fear into the heart of a diesel truck owner quite the way these do. It starts small: a simple shudder or vibration. But before you know it, you're white knuckled, grasping the steering wheel tight, trying to settle the truck down before losing control.
While the causes and cures of death wobble are a highly debated topic, if your truck has it, there is no mistaking it. The first step in controlling death wobble is understanding exactly what it is. Death wobble is used to describe a series of sudden, often violent, front suspension vibrations exhibited by solid front axle suspensions, and more infrequently, independent front suspensions. When death wobble occurs, you will feel a shaking in the steering wheel, which will increase or decrease with speed, and depending on severity, shaking throughout the cab. If you experience death wobble, let off the accelerator and allow the truck to slow down until the vibration stops, then immediately proceed to a safe place where the vehicle can be inspected before continuing on. Even just one death wobble incident can cause permanent-and dangerous-suspension or steering damage.
It is important to understand that there is no single problem that causes death wobble. Rather, any combination of things, such as tire balance, loose bolts, worn bushings, bad alignment, and even tire pressure can trigger the condition. Correcting death wobble is often a slow and meticulous process of elimination. The first order of business is to rule out the simple things. Look for clues, such as mismatched tire pressure, uneven tire wear, or play in the steering system. Next, crawl under the truck and check for loose bolts, fresh rust, or wallowed-out bolt holes, paying special attention to the track bar brackets. We've taken some of the guesswork out for you and have listed 11 of the most frequent causes of death wobble.
Tire Pressure
The very first step in diagnosing any form of death wobble is checking tire pressure. Under-inflation, over-inflation, and mismatched pressures are all potential triggers. A recent study by the Rubber Manufacturers Association shows that only 15 percent of Americans know how to properly check tire pressure. A great starting point for proper inflation is listed on the vehicle's doorjamb sticker-even for vehicles with over-sized and off-road tires.
Tire Balance
When was the last time you had your tires balanced? Most people balance tires one time: when they are first mounted on wheels. Realistically, tires need this treatment more frequently than any of us would like to admit. As a tire wears, its weight and proportions change, if only slightly, causing a mild, out-of-balance condition over time. Conversely, a properly balanced tire may lose some, or all, of its wheel weights, which may trigger the death wobble condition. Balancing and rotating tires at each oil change will help prevent this condition from beginning and help immensely with tire wear.
Alignment
Another major trigger is improper steering alignment. We use our trucks-hard. Sled pulling, off-roading, four-wheel-drive launches, and daily battles with potholes all punish steering and suspension components. Over time, these parts can become loose, worn, or worse: bent and broken. Proper alignment ensures you continue rolling down the road straight and minimizes the potential for death wobble.
Often overlooked, out-of-spec caster is a leading cause of death wobble. Lift, leveling, and lowering kits all alter the amount of caster that is present. Fortunately, a proper alignment-with the addition of caster cams-will usually get you back in the proper spec. This is one of the most commonly overlooked items when a lift kit is installed.
Track Bar
Death wobble can most often be traced back to the track bar. The track bar's job is to locate the front axle under the truck. Because the track bar attaches at one end to the frame, and the opposite to the axle, it is subjected to significant loads as the steering and suspension cycle. Once any of its components have been compromised-such as bolts, bushings, or bracket welds and mounting holes-it can transfer vibrations and start the oscillations that eventually become death wobble. An adjustable, or upgraded track bar is always a good idea when any type of lift kit is installed.
Tie Rod
The tie rod connects the steering knuckles and transfers input from the drag link to the wheels. Adding larger, off-road tires can increase stress on the factory tie rod. Worn rod ends and bent tie rods can cause the telltale signs of death wobble: steering wheel shake, chassis vibration, and wandering. A good tie rod will have adequate rotational movement at the joint but will not have any up-and-down or side-to-side play. Heavy-duty tie rods and rod ends are readily available in the aftermarket and are more resistant to loads from the addition of larger tires.
Drag Link
The drag link is the rod between the pitman arm and your knuckle. It's what transfers steering input from the steering box to the knuckle. You'll want to examine the drag link for signs of damage, such as bends, and the condition of the joints on each end. There shouldn't be any up-and-down play in these joints. Heavy-duty drag links and joints are available from several aftermarket companies.
Ball Joints
Ball joints are one of the critical components of any steering and suspension system. They not only act as the pivot between the steering knuckles and the vehicle's suspension, but they are also responsible for handling the enormous amount of load and force the vehicle sees daily. When ball joints wear out, they can cause unwanted movement from the wheels and tires, transferring that vibration to the chassis. Adding larger wheels and tires-and the extra weight that comes with them-can easily exceed the factory ball joint's limits, causing accelerated wear. We recommend greaseable, heavy-duty, rebuildable, ball joints as replacements for the factory units. While not cheap, these will save you from many headaches down the road. To check for ball joint wear, lift one corner of the vehicle and grab the tire at the 12- and 6-o'clock positions. Rock the tire back and forth while looking for play at the ball joints; there should be none.
Steering Damper
Often referred to as a steering stabilizer, the steering damper helps absorb unwanted secondary vibrations that can trigger death wobble. A steering damper is not a fix for death wobble, but it's still an important part of the steering system that should be checked regularly. As the factory damper wears out and larger tires and wheels are added, a stouter unit may be needed. While many replacements are available, they are not all created equal. Be sure to order a damper that is designed for steering, as some companies sell units that are merely normal shock absorbers, designed to be mounted vertically. The issue with this arrangement is that when these units are mounted horizontally, they can experience a change in resistance throughout the stroke. Also watch for nitrogen-charged dampers, as they can place unwanted pressure on one side of the vehicle. A good steering damper has linear resistance throughout the entire stroke. Shop BD Diesel Brand Steering Box Stabilizer for 2003 to 2018 Dodge RAM
Control Arm or Leaf Spring Bushings
Whether you have stock rubber bushings, polyurethane, or spherical bearings, such as Heim joints or uniballs, they should all be inspected regularly for any wear or damage that would allow for excess movement in the control arm or leaf pack. Also check for loose bolts and wallowed-out bolt holes; both of these would cause undue movement in the suspension. On trucks with a leaf-sprung front suspension, pay close attention to loose or damaged U-bolts, as these could allow the axle to freely move under the chassis.
Wheel Bearings
Wheel bearings support the load of the vehicle and allow for the wheels to turn smoothly. A sure sign of worn-out bearings is side-to-side play, vibration, and even a grinding or squealing noise. On older vehicles with traditional, serviceable, wheel bearings, it is important that they are adjusted properly and greased regularly. Newer vehicles equipped with unit bearings should also be checked at regular intervals, and if signs of wear exist, the bearing should be replaced. To check for bearing wear, lift one corner of the vehicle and grab the tire at the 3- and 9-o'clock positions. Rock the tire back and forth looking for any signs of movement not associated with steering linkage.
Steering Box
After chasing all the usual death wobble suspects to no avail, sometimes you'll discover that the issue is in the steering box itself. Worn-out internal parts can cause slop in the steering, and a bent or twisted sector shaft can increase the effort required to turn the wheel and limit the range of motion, increasing turning radius. Many steering boxes have adjustment built in to reduce play between the worm gear and sector shaft teeth. However, once an adjustment is made, the gears will wear at a quicker rate, ultimately leading to replacement of the box.
IFS and Death Wobble
You may have noticed that most of the causes and cures we discussed are related to trucks with a live-axle front suspension. Typically, death wobble is an issue that plagues these vehicles, making Ram and Ford trucks more susceptible than GM's current offerings. This happens due to the fact that in a live-axle system both front tires are connected to each other via the axle tube, while an independent front suspension isolates the two rotating masses from each other. That being said, IFS trucks can and do still suffer from the effects of death wobble.
Should your IFS truck develop a death wobble condition, diagnosing the cause is the same as described for live-axle trucks. Methodically check tire pressure, balance, and front-end alignment. From there, move to the tie-rod ends, steering centerlink, and pivots. And lastly, examine bushings, ball joints, and bearings.
Technically Speaking
Though we use it as a technical term, the phrase "death wobble" is something that's made up. It is widely used to describe a combination of several different steering, alignment, and balance-related issues, specifically, tramp and shimmy. The other term most often misunderstood when discussing death wobble is caster. Listed below is a quick explanation of each of these terms.
Shimmy: Shimmy is a condition in which the front tires move in and out, or vibrate, at certain speeds. This is noticeable in the steering wheel as a jerk, left and right.
Tramp: Tramp is a condition in which the front tires move up and down, in a bouncing motion. This condition is noticeable in the steering wheel as a vibration.
Caster: Caster is one of the three main alignment specs: caster, camber, and toe. Unlike camber and toe, however, caster does not contribute to tire wear but instead is used to achieve the self-centering action of the steering. Caster angle is the difference between an imaginary line that runs through the centerline of the upper and lower ball joints, and vertical.
Orginaly Published in Truck Trend May, 2013