Death Wobble
#1
04-02-2008, 09:17 PM
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Death Wobble
Recently purchased a 2008 f350 crew cab longbox diesel. It has a 4 " skyjacker lift kit and 18000 miles. Today on the highway at 60mph the truck started bucking and shaking so violently I had to pull over to the side of the road. The motion was so violent , if I was not on a divided highway, I would have gone into on coming traffic. I am by no means a mechanic or "truck guy", so I had no idea what had occurred. After driving home slowly, and cleaning my shorts, I goggled ford wobble and found out about the dreaded Death Wobble. I am glad I am not alone with this. As today is the first time it has happend to me ( I bought the truck last week ), what are my options? I know this has happened to many owners and would like to know what my first step should be? Read many sites about fixing it has confused me a little. Is this only a problem with lifted trucks? Most importantly, how can it be fixed? Thanks to all in advance.
#2
04-02-2008, 09:28 PM
#3
04-02-2008, 09:40 PM
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Krewat, "Death Wobble" is generally caused by a suspension absorbing blows from the road laterally or front to back, rather than up and down (like it is supposed to). Also, and I say this in general, the likelihood of experiencing this phenomenon is increased as the suspension is lowered away from the truck. Primarily on Coil sprung, straight axle setups. Most brands have experienced this...Dodge, Ford, Jeep, all the ones using coils and "lateral" bars.
Ford has some service bulletins out on how to fix this, but they are all minor fixes to a design flaw. Air pressure adjustments, alignment, tow in/out, etc. All are shots in the dark in my opinion. This is one aspect of having a leaf spring that are superior (one of the few) and I cling to it! haha!
Ford has some service bulletins out on how to fix this, but they are all minor fixes to a design flaw. Air pressure adjustments, alignment, tow in/out, etc. All are shots in the dark in my opinion. This is one aspect of having a leaf spring that are superior (one of the few) and I cling to it! haha!
#4
04-03-2008, 09:30 AM
Originally Posted by josh04hdf250
This is one aspect of having a leaf spring that are superior (one of the few) and I cling to it! haha!
Me, I have leaf springs. Stock, with a stock stabilizer that had already leaked it's guts out, I had some very bad bump-steer, so bad it would wind up in the next lane if I was going around a curve.
Rancho stabilizer got rid of it, but better shocks also made a big difference.
To some, stabilizers are a band-aid. To me, they are a necessity in any high-unsprung-weight vehicle.
#5
04-03-2008, 09:56 AM
#7
04-03-2008, 02:21 PM
Ford has some service bulletins out on how to fix this, but they are all minor fixes to a design flaw. Air pressure adjustments, alignment, tow in/out, etc. All are shots in the dark in my opinion. This is one aspect of having a leaf spring that are superior (one of the few) and I cling to it! haha!
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#8
04-03-2008, 03:55 PM
My opinion on most of the "death wobble" is that it's a resonance set up in the steering box, where the front suspension is pushed one way, the steering box reacts and pushes back, but too far. It travels the other way, the box catches it again, and pushes back the other way, again too far. And so on, and so on.
Alignment, tire pressure, and so on can get rid of that sweet spot where the resonance occurs. But it's a moving target.
Anyway.. I've heard of leaf-sprung Superduty's with the same type of issue.
Alignment, tire pressure, and so on can get rid of that sweet spot where the resonance occurs. But it's a moving target.
Anyway.. I've heard of leaf-sprung Superduty's with the same type of issue.
#9
04-03-2008, 05:47 PM
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#11
04-03-2008, 06:49 PM
Krewat, maybe we are refering to the same thing, just describing it differently. This is my theory on what people are calling death wobble. If if sounds like I am talking down to anyone I am not. The following paragraphs I have cut and pasted from a discussion I had with a 4x4 newbie, which I know very well that you are not a newbie. The following discussion also deals with the 05-07 trucks, though the priciples are the same. In the instance of Luckeyjeffs rig, I would look to loose track bar bolts since they are often undertorqued by inexperienced installers, and after that I would start looking hard at the specific components of the lift to make sure that the kit was installed properly. A properly designed, properly installed kit often rides better than stock, not worse.
In my opinion the symptom not-so-fondly named "death wobble", in this particular instance, would be more appropriately classified as "bump steer". Bump steer is a very common occurance in lifted vehicles and is caused by steering geometry that is changed when you drop the front axle in relation to the frame of the truck. More specifically, it is directly related to the position of your steering centerlink in relation to the track bar.
Trac bar - 101. The trac bar is a rigid bar that extends from one side of the frame of the vehicle down to the axle on the opposite side of the vehicle. This keeps the axle firmly oriented under the vehicle, preventing it from shearing off under side loads. Without a trac bar, the only thing keeping your axle from going side to side are the bolts on the springs which are woefully under rated for that task. When you have a rigid track bar in place the axle acually moves side to side under the truck as the suspension compesses. This is because while the bar holds the axle firmly, it also forces it to travel in a mild arc. Your front axle actually moves side to side under the truck as much as an inch (under severe wheel travel) when the suspension compresses up and down over bumps. Bump Steer happens when the arc created by the axle differs from the arc created by your steering centerlink. The steering centerlink acts similar to a trac bar because as the suspension flexes, it too travels in an arc. When the axle is moving side to side becuase of the trac bar, the tires actually twist from left to right becuase of the arc created by the steering centerlink. So, if the axle moves an inch, and the steering centerlink only moves say 3/4 of an inch, this means that the tires are twisting left to right a few degrees simply because you hit a bump. This is felt in the steering wheel in mild cases as oscillation and in extreme cases as this wild violent shaking.
In order to minimize the effects of bump steer, you want to accomplish two things, one, you want your track bar to be roughly the same lenth as your steering centerlink, and two, you always want it to be perfectly parallel to your steering centerlink. Doing this makes the two travel in in the same arcs and minimizes bump steer yada yada. Getting back to the case in point. On the 05-06 superduty trucks, ( at least all the ones I have been able to examine) the track bar is approx. 6 inches shorter than the centerlink and where it mounts to the frame it is about an inch and a half too high in relation to where the centerling moints to the pitman arm. This translates into dramatically different arcs of travel and would seem to me to be a likely cause of the violent shaking on bumpy roads. I doubt that any amount of part swapping will do anything to resolve this problem becuase in my opinion, it is a design issue.
How to fix this problem? One could make a dropped trac bar mount for the frame side of the trac bar that would move the mointing point down around an inch and a half to make it parallel to the centerlink. This would not totally fix the problem, but would likely help. The last thing to do, and this would be difficult, but if one could adapt the 05-06 superdutys to use the tie rod ends and centerlink that the 99-03 superdutys used, this would mean a shorter overall centerlink and when combined with a lower track bar mount, it should virtually eliminate all bump steer.
My idea is based on a few assumptions which may or may not be correct.
1. The largest percentage of vehicles with this problem are 4x4 trucks.
2. Most of the vehicles that do it, do it right off the dealer lot (even if it doesn't happen isntantly is no reason that it couldn't, given the right set of bumps)
3. Many owners of 4x4 trucks do experience this problem to varying degrees
4. Dealers often have troubles repeating this problem because the issue is directly related to wheel travel on the passenger side of the truck. ( if you hit a bump on the drivers side, you will obviously feel the bump, but you won't have the axle traveling in an arc like you would if it hit a bump on the passenger side, so no bump steer)
5. Dealers often don't know a lot about steering geometry becuase they are an OEM shop. They don't do suspension mods so they haven't had to learn the sciences behind steering and suspension geometry like a custom 4x4 shop would, and therefore wouldn't even think to consider geomety as an issue.
6. Lastly, becuase so many people have this issue and none of the dealers have completely resolved it, to me that would indicate that it is not so much a faulty component issue, but would more likely be a design and engineering issue.
Trac bar - 101. The trac bar is a rigid bar that extends from one side of the frame of the vehicle down to the axle on the opposite side of the vehicle. This keeps the axle firmly oriented under the vehicle, preventing it from shearing off under side loads. Without a trac bar, the only thing keeping your axle from going side to side are the bolts on the springs which are woefully under rated for that task. When you have a rigid track bar in place the axle acually moves side to side under the truck as the suspension compesses. This is because while the bar holds the axle firmly, it also forces it to travel in a mild arc. Your front axle actually moves side to side under the truck as much as an inch (under severe wheel travel) when the suspension compresses up and down over bumps. Bump Steer happens when the arc created by the axle differs from the arc created by your steering centerlink. The steering centerlink acts similar to a trac bar because as the suspension flexes, it too travels in an arc. When the axle is moving side to side becuase of the trac bar, the tires actually twist from left to right becuase of the arc created by the steering centerlink. So, if the axle moves an inch, and the steering centerlink only moves say 3/4 of an inch, this means that the tires are twisting left to right a few degrees simply because you hit a bump. This is felt in the steering wheel in mild cases as oscillation and in extreme cases as this wild violent shaking.
In order to minimize the effects of bump steer, you want to accomplish two things, one, you want your track bar to be roughly the same lenth as your steering centerlink, and two, you always want it to be perfectly parallel to your steering centerlink. Doing this makes the two travel in in the same arcs and minimizes bump steer yada yada. Getting back to the case in point. On the 05-06 superduty trucks, ( at least all the ones I have been able to examine) the track bar is approx. 6 inches shorter than the centerlink and where it mounts to the frame it is about an inch and a half too high in relation to where the centerling moints to the pitman arm. This translates into dramatically different arcs of travel and would seem to me to be a likely cause of the violent shaking on bumpy roads. I doubt that any amount of part swapping will do anything to resolve this problem becuase in my opinion, it is a design issue.
How to fix this problem? One could make a dropped trac bar mount for the frame side of the trac bar that would move the mointing point down around an inch and a half to make it parallel to the centerlink. This would not totally fix the problem, but would likely help. The last thing to do, and this would be difficult, but if one could adapt the 05-06 superdutys to use the tie rod ends and centerlink that the 99-03 superdutys used, this would mean a shorter overall centerlink and when combined with a lower track bar mount, it should virtually eliminate all bump steer.
My idea is based on a few assumptions which may or may not be correct.
1. The largest percentage of vehicles with this problem are 4x4 trucks.
2. Most of the vehicles that do it, do it right off the dealer lot (even if it doesn't happen isntantly is no reason that it couldn't, given the right set of bumps)
3. Many owners of 4x4 trucks do experience this problem to varying degrees
4. Dealers often have troubles repeating this problem because the issue is directly related to wheel travel on the passenger side of the truck. ( if you hit a bump on the drivers side, you will obviously feel the bump, but you won't have the axle traveling in an arc like you would if it hit a bump on the passenger side, so no bump steer)
5. Dealers often don't know a lot about steering geometry becuase they are an OEM shop. They don't do suspension mods so they haven't had to learn the sciences behind steering and suspension geometry like a custom 4x4 shop would, and therefore wouldn't even think to consider geomety as an issue.
6. Lastly, becuase so many people have this issue and none of the dealers have completely resolved it, to me that would indicate that it is not so much a faulty component issue, but would more likely be a design and engineering issue.
#12
04-03-2008, 09:14 PM
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#13
04-03-2008, 09:44 PM
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So....has anyone actually discussed this directly with Ford or their dealer and is there a fix for a stock 05+ truck? It sounds like this can lead to a serious lawsuit as it seems this problem has been around for some time. I mean, why hasn't this kind of thing been made more aware of? Sounds like a real serious defect.
#14
04-03-2008, 10:08 PM
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#15
04-03-2008, 10:46 PM
So....has anyone actually discussed this directly with Ford or their dealer and is there a fix for a stock 05+ truck? It sounds like this can lead to a serious lawsuit as it seems this problem has been around for some time. I mean, why hasn't this kind of thing been made more aware of? Sounds like a real serious defect.
The most common solution for the older (05-07) trucks is to ensure that the tire pressure up front is adequate. This is not so much a solution, as it is a means of mitigating the chances of an incident. The front tire pressure on our trucks needs to be at least 55 psi or higher. Some individuals have also found improvement by uprading thier tires and/or shocks.
Next step is to have the vehicle realigned according to the TSB mentioned earlier in this thread. This does seem to help as well.
The last more permanent "fix" is the installation of a quality dual steering stabilizer setup. Based on the reasons I stated earlier, I would call this a fix for the symptoms, and not a fix for the illness, but it is a "fix" nonetheless, and every individual that has done so has reported that the problem has all but been eliminated.
Based on the fact that there has been many many individuals who have replaced tons of almost new components with no resolution, I am a firm believer that this problem in stock trucks is as I stated, a design problem and can not be trully fixed without rejiggering things a bit, but I also have come to see that through proper front end maintenance, and the dual stabilizers, the condition can be managed to the point I would call it adequate for safe daily use.
In the case of the original poster, his truck is not stock, and the stock geometry does not exhist. He, and others like him (with lifted trucks) who may have this problem should probably bypass the stealership and have the truck looked at by a quality 4x4 shop that is familiar with lifted trucks and the ensuing problems that can happen.