What Causes A Death Wobble Video On An 1980s Peterbilt 359
Above is a quick video about what a death wobble looks like in real-time.
This video perfectly demonstrates what you call a death wobble. It’s called a death wobble because you think you’re going to die when it starts happening.
This truck is pretty cool, and I just love the looks of this old truck. It’s a 1980s vintage Peterbilt 359, and it’s in mint condition.
The customer’s original complaint about this truck was that it had a shake and a loose king pin.
What is a death wobble?
Death wobbles come from a strong axle with low load rate springs.
Typically the springs are strong enough to twist the axle when the tire hits a bump in the road but does not have enough strength to dampen the torsional movement of the axle.
This results in the king pin angles moving in opposite directions, causing your suspension or steering to shake violently.
Typically the vehicle must be brought to a complete stop for the death wobble to subside.
We started with the steering components.
So we first want to repair what we know is a problem on the truck with the loose king pin. That’s the first place to start.
As we tear it down, we find out that this truck’s solid front axle has been bored where the kingpin goes through.
In fact, it’s bored big enough that where the axle goes around the kingpin, it’s starting to spread. It’s not too far from that kingpin getting ready to split out the axle’s end and lose a wheel.
Unfortunately, this is an old enough truck that the front axle under this truck was discontinued. According to Peterbilt, no axle is made as a replacement for this vehicle.
After a little investigation, we came up with an axle that could be used as a replacement. However, it took some ingenuity with fabrication and modifications of the axle mounting to put it all together.
After we got it all together, we went for a test drive, and it drove nice and smooth.
We can run this truck at any highway or local speed, and it runs smoothly down the road without problems. So we send it back to the customer, and he drives it for a few days.
After the first couple of days of driving, he’s got the same report. This thing drives like a dream. It’s nice and smooth in the front end, and it drives better than it’s ever driven before.
Next, we had to reevaluate the suspension system.
However, on the third day of driving it, he starts to get his shake back again. And it’s not just any shake. This shake is triggered when you hit some potholes at the right speed on the road.
It’s something called the death wobble. The reason it’s called a death wobble is because when it starts happening, you think you’re going to die.
So first off, we took a camera and mounted it back behind the passenger tire. Using a camera allowed us to get a visual idea of what was happening at road speeds with the following:
- suspension parts
- steering linkage
- tires and wheels
It did take us several miles of driving around to get the footage we needed.
Once we reviewed the video, we could see something wasn’t right in the truck’s left front.
Next, we mounted a camera behind the front bumper, pointing toward the driver’s side tire. This allowed us to get a good look at what was happening with the wheel, steering, and suspension on this truck.
Once we did this, we got a better view of what was happening. As we slowed the video down, we could see the airbag dancing back and forth on top of the axle. We could even see the axle being twisted a little bit.
Finally, the problem and repair
After taking a closer view at an even slower speed, we noticed a little bit of movement on the front spring. A worn spring pin bushing was causing this movement.
The worn spring pin bushing allowed the spring to twist back and forth, initiating the death wobble.
Once a new bushing and set of shocks were installed, we test-drove the truck, and the death wobble was eliminated.
If you experience a death wobble, remember to contact Wayne Truck & Trailer, where we provide solutions for the road ahead.
Check Out More Truck News
Tips To Evaluate Frame Repair Damage On Semis & Dump Trucks
