If you have spent much time looking into off road suspension, lift kits or even just owned a Jeep, no doubt you have heard of “death wobble”. But what is death wobble? What causes it? How can a vehicle that drives fine one day all of a sudden be un-drivable the next? How can a brand new Ford Superduty have death wobble?? Well that is what we are going to cover!
First off, what is death wobble defined as? Well, when you experience it there is no doubt in your mind that is is death wobble! But if you are lucky enough to not have experienced it then the feeling of it would be described as the wheel violently turning back and forth in your hands with no way to control it, or the vehicle for that matter. The only thing you can do is to try to slow down safely until the wobble subsides. Often times it is brought on by hitting just the right bump at just the right speed.
Now death wobble is not the same for all vehicles. For instance, I have driven vehicles where it will only happen at 55-60 mph and I have also driven vehicles (Jeeps) that will do it at 10-15 mph. Now why is that the case?
There are many factors that can cause death wobble. Sometimes it is one big issue and sometimes it’s a number of smaller issues that can add up to it. For the most part death wobble occurs from worn out suspension and/or steering components. The first place we like to look is the track bar, also known as the panhard bar. A worn out bushing or rod end can cause the front end to have too much play side to side and induce death wobble.
We check this by getting under the vehicle and with it off but the key on, to free up the steering wheel, have someone saw the wheel back and forth while you look at both ends of the track bar. You are looking for any excessive movement out of the joints. A worn rod end or hiem will cause play that will contribute to the wobble. Sometimes an older factory style rubber bushing will have too much play or be worn and cause too much movement.
If you see that there is too much play in the track bar bushings or rod ends, it is time to replace them or the entire bar depending on your setup.
The next parts we look at are all the steering joints. The procedure for checking these is the same as the track bar. Get under the vehicle and have a friend saw the wheel back and forth and look at each tie rod end and draglink end. If you see any play in these then it is a good idea to replace them. Also make sure to look at the pitman arm connected to the steering box. These can sometimes come loose and “walk” on the sector shaft in the steering box. Make sure the pitman arm nut is tight and the pitman arm does not have movement. Also pay attention to the sector shaft itself. The bearings in the box can wear and cause that shaft to have movement. Again, leading to or contributing to death wobble.
The next thing to check, and probably the easiest and most over looked, is the castor. Castor is the measurement, or angle, at which your axle is angled back. Really the inclination of the upper and lower ball joint. You will want your castor to be towards the back of the vehicle. Weather you call this negative or positive castor really doesn’t matter. You will NEVER want your castor to be angled toward the front of the vehicle. So when we refer to castor, we are always referring to laying the castor back (Positive Angle).
We have found that, especially on Jeeps, when a lift is installed a lot of times it will throw off the castor and make it too shallow. We see this a lot with short arm lifts that have no adjustability. This is why we try to build adjustment into our products like our Ford Superduty Radius Arms.
When we set castor we like to see it around 4-4.5 degrees. This will help with self centering of the wheel and give you a nice stable handling. When you go shallower than that, 2-3*, you will experience more of a wandering feel. The vehicle will be a little harder to keep straight without small adjustments and the wheel will feel very light and not want to return to center on its own as easily. This shallow castor is also a large factor leading to death wobble!
Make sure to check your castor! Usually this can be addressed with adjustable links or leaf spring shims. But sometimes due to driveline angle issues you will need to take a more drastic step. You may have to cut and turn the inner C’s on your axle. We won’t go over that in this post but there was a great article that Harry Wagner wrote in Crawl Magazine “Knucklehead”, where we did a cut and turn on his big Ford Raymond. We will make a more in depth post about this subject later.
So in short, death wobble is not a fun thing to experience and may sound like a scary and impossible problem to fix. But it is not! Make sure that your rigs suspension is all tight and well taken care of. Look for any loose joints and make sure your castor is in spec! Sometimes it can be a very small amount of movement from many parts that will add up to a bigger problem and cause that dreaded death wobble. But don’t let it beat you!
Let us know if this helped you and if there are any other topics you would like to see us address!