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Old 04-09-2015, 11:39 PM   #11
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Re: Death Wobble - Possible Resolution

Below is a modification of what I posted here:

http://www.ford-trucks.com/forums/12836 ... 40mph.html

The best thing about that post, was that one of the persons whom I most respect at FTE, Cleatus12r, agreed with me. He also made a comment about ladder bars, which may pertain to you.

OK, I will get flamed for what I am writing below. It is considered heresy, but it is based on my extensive personal experience with DW and how I eventually cured it.

First, don't focus on what "initiates" the DW. You can and should fix that (i.e., by replacing a warped rotor, replacing a warn bushing or ball joint, etc.). But if your set up has the propensity to "propagate" DW then something else will initiate it, and you will be chasing down that initiating event, rather than curing the DW from propogating. (I mean it is not a single isolated bump steer that scares you correct? It is the resulting "wobble" back and forth that can kill you going downhill into a turn on an icy road with a big rig coming towards you uphill or when you are going downhill pulling a tandem one yard concrete mixer. Both of which I have experienced with DW.)

Adding the Energy Suspension track bar bushing and tightening up the steering box (both of which I did) just makes the propagation more efficient and more likely to oscillate more violently.

So here goes, IMO, "Death Wobble" is caused by one tire (e.g., the left) hitting a bump and pushing through the tie rod up against the rubber sidewall (which is, effectively, an undampened spring - it is rubber filled with air after all -- you know how a rubber basketball filled with air bounces?) of the right tire causing a "bump steer" to the right resulting in a reaction of the right sidewall springing/pushing back through the tie rod to the rubber sidewall of the left tire which repeats with increased violence until the vehicle stops or nearly stops rolling. This is best seen in your third video - Ultra Low Speed - where you can see that the tie rod is moving left and right while, as a reference, the differential immediately behind it is relatively stationary:



That is the oscillation commonly called DW. The steering wheel vibrates violently back and forth as the tires violently wobble side to side, one tire punching the sidewall of the other tire and that tire punching back through the ineffectively dampened tie rod.

The reason that tightening up my steering box or replacing the track bar bushing caused my DW to actually get worse is because those things actually increase the effectiveness of the bump steer by tightening up the suspension!

In my experience of chasing down Death Wobble, it has nothing to do with the track bar, ball joints, or caster. It is merely an undampened spring (with the air-filled rubber sidewalls of the two front tires being the springs). Yes, find and replace worn components, I am only saying some brand new Fords and Dodges with coil springs and solid axles have DW right from the factory - brand new!

So, after avoiding DW for only one year after $3,000 of front end work and a set of brand new tires (Toyo Open Country AT's), at TurboStew's suggestion (see link to his post below), I installed dual opposing Bilstein gas PRESSURIZED SHOCKS (not stabilizers) using a Rough Country dual stabilizer bracket which I cut up and re-welded for a custom fit. And in thousands of miles all over the Western US and Southern B.C., I didn't have a DW since.

http://www.sportsmobileforum.com/viewto ... 9&start=15

BTW, the opposing gas pressurized shocks push against each other thereby cancelling each other out and, thus, do not put any pressure on the steering box while an opposing dual stabilizer set up (a stabilizer has resistence both pushing in and pullling out) would create tremendous resistence on the steering box (possibly causing premature wear and looseness).

In summary, for those of you who have had DW, you wouldn't drive your truck without vertical shocks at each wheel to dampen the sprung mass of the body, would you?

So why would you drive your truck without horizontal shocks connecting the tie rod to the differential to dampen the horizontal spring effect of the rubber on those big sidewalled tires you are putting on the front of your truck?

Finally, anyone who says that dual opposing gas pressurized shocks used as a steering stabilizer are just "masking" the underlying problem is . . . in polite words: "mistaken."

For those of you who believe that . . . , please take off the vertical shocks at each of the four wheels on your truck and see if you like driving it while it bounces uncontrolably up and down without the benefit of "masking" which the vertical shocks provide by dampening the vertically sprung mass of your truck's body.

On a stock van, the hydraulic steering box is the only tie rod dampener. It is marginal at best and cannot provide sufficient dampening with a larger than stock tires or with 4x4 hubs or larger brake rotors added to the wheels. Both larger tires and 4x4 lockout hubs and larger brake rotors add mass at the end of the tie rod which the stock steering box cannot dampen effectively.

You added hydro steering. I thought of that too. Because hydraulic steering is hydraulic it inherently provides extra tie rod dampening to that provided by the hydraulic steering box. (But hydro is from what I read great for slow speed rock crawling but can cause unpredictable immediate lane changes at highway speeds, so I passed.) I provided the required additional tie rod dampening as described in the sportsmobileforum.com thread above. Your set up is extreme and in my limited experience needs extreme tie rod dampening. So, you may want to add what Turbostew and I did to your set up as well.

As far as whether or not increasing the sidewall height of the front tires by going to a bigger tire would increase the likelihood of DW or not, I prefer not to speculate. The internet is an echo chamber of misinformation. I have read lengthy posts by people who have never had Death Wobble telling other people who have it that it is their track bar or their ball joints or their caster -- even on brand new F350's!

I already mentioned spending $3,000 with the 4x4 converter only to have the DW return in 2 years. The only thing that made it go away for a while was replacing the front tires (with half the tread left!) with new ones (Toyo AT's). I then bought a used 600lb. Snap-on torque wrench and checked my track bar bushings myself. They were fine (they were only 2 years old after all).

Then I found TurboStew's post on the opposing dual gas pressurized Bilstein shock absorber steering dampener set up and in the years since installing it, I have not had DW once.

How much you want to bet that if I drove my van without the opposing dual gas pressurized Bilstein shock absorber steering dampener that I would have DW immediately again?

Finally, IMHO, there should be a moratorium on people who have never had DW from suggesting to others how to fix it.

[Flame suit on, visor down...]
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Old 04-10-2015, 04:20 AM   #12
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Re: Death Wobble - Possible Resolution

Quote:
Originally Posted by E350

Finally, IMHO, there should be a moratorium on people who have never had DW from suggesting to others how to fix it.

[Flame suit on, visor down...]
With such a well-presented opinion and practical experience sharing I would be one of your staunch defenders that your contribution is far from heresy or not pertinent to this dangerous condition.

Because I also agree with your suggested moratorium I have absolutely nothing to add here other than providing a link to an article how to properly adjust the pinion gear backlash of the steering box: http://www.ford-trucks.com/forums/12...one-right.html.

(Instructions in that link are wonderfully excerpted from a larger procedure however what's presented is more than enough to perform this action. That info can be found here: http://www.stangerssite.com/adjustment.html)

As can be seen it entails a bit more than a trial and error method. I'd venture to say most DIY's without the proper tools should avoid this as improperly done it would contribute to premature failure of the steering box.
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Old 04-10-2015, 06:45 AM   #13
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Re: Death Wobble - Possible Resolution

thank you for posting up the additional pix.

i just dont understand how your getting so much front to back movement. especially with poly bushings.

that said, my particular vans death wobble is initiated differently than yours. so maybe i dont have the official death wobble i read so much about. hitting potholes doesnt seem to affect my van all that much. sure, it can be harsh, but it doesnt affect the way the van handles. im thinking my issues come from slow steering response. i have zero issues till higher speeds, like above 60-65 mph. even at those speeds, potholes and imperfections in the road dont seem to affect our van that much. its the steering imput and how late it takes to react, then chasing that late reaction, and so on.

it would be really interesting to see some vids from other van conversions, especially the different vans people have complaints with the wobble. i know ill be doing one here very soon. that was a great idea

also, very curious about the not adjusting your set screw on the steering box. why would it not be ok to adjust that? ive messed with that setting on many vehicles to tighten up the slop. at times, ive done massive adjustments compared to what others have done. seriously, i think i tightened up the set screw a good 5-6 turns on our van when i first got it hoping to get rid of the slow steering response.
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Old 04-10-2015, 07:03 AM   #14
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Re: Death Wobble - Possible Resolution

I would recommend more castor, +5-6 degrees is ideal.
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Old 04-10-2015, 08:00 AM   #15
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Re: Death Wobble - Possible Resolution

Quote:
seriously, i think i tightened up the set screw a good 5-6 turns on our van when i first got it hoping to get rid of the slow steering response.
The reason you don't want to adjust it too much is because of the stress it puts on the gear. Sure, you can get rid of the slop but then you will prematurely wear the gear in the areas where it sees the most action (when you are about +/-10 degrees of steering wheel motion.) As the middle wears faster you then go to make turns and you are wearing the other part of the box evenly. This creates uneven wear in the system and gives you slop in the center section. You then turn the screw in a few more times and this repeats until you have failure.
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Old 04-10-2015, 08:03 AM   #16
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Re: Death Wobble - Possible Resolution

Quote:
Originally Posted by UJOINT
I would recommend more castor, +5-6 degrees is ideal.
I should be close to 6 degrees of caster later today. I think that will help the situation but I do not think that is causing the wobble. I am sure it is going to improve highway drivability at a minimum and from what I hear the drawback to high caster is more steering resistance at low speed, sharp turns but I have hydraulic assist to take care of that.
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Old 04-10-2015, 08:19 AM   #17
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Re: Death Wobble - Possible Resolution

Quote:
Originally Posted by E350
In summary, for those of you who have had DW, you wouldn't drive your truck without vertical shocks at each wheel to dampen the sprung mass of the body, would you?

So why would you drive your truck without horizontal shocks connecting the tie rod to the differential to dampen the horizontal spring effect of the rubber on those big sidewalled tires you are putting on the front of your truck?

Finally, anyone who says that dual opposing gas pressurized shocks used as a steering stabilizer are just "masking" the underlying problem is . . . in polite words: "mistaken."
Interesting treatise.

Something to consider though in your analogy to the vertical shocks at each wheel: The vertical shocks dampen the oscillation or movement between the sprung and unsprung masses - not the "spring effect of the rubber on those big sidewalled tires", nothing dampens that except the tire itself.

You are suggesting that the "horizontal shocks connecting the tie rod to the differential [s:10obkgs7]to[/s:10obkgs7] dampen the horizontal spring effect of the rubber on those big sidewalled tires" - again, nothing dampens that except the tire itself.

What the "horizontal shocks" dampen is the rotation of the steering knuckles on the ball joints steering axis - and the transfer of that rotation to the other steering components.

Death Wobbles are the uncontrolled rapid rotations of the steering knuckles on the ball joints steering axis - for whatever reason. Whether that rotation is caused by design constraints, worn components, alignment issues or "tire spring" the steering damper are just "masking" the "problem".

Look to gyroscopic inertia around an ever changing spin axis for an understanding of DW's - that is why DW's are rotational speed sensitive (speeding up or slowing down the vehicle will stop DW's) and steering angle sensitive (turning will stop DW's).

Bigger tires have greater gyroscopic inertia, worn components, a different scrub radius due to wheel offset, and other designed in factors create an ever changing spin axis all contribute to Death Wobbles.

Sometimes, after repairing everything that can be repaired and replacing everything that can be replaced, Death Wobbles still exist because of design characteristics that you cannot change - then "masking" with Steering Dampers is totally acceptable.
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Old 04-10-2015, 08:28 AM   #18
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Death Wobble - Possible Resolution

Sidetrack06-sorry off topic. I'm about to have Don at Boulder Offroad do some work and want to get your opinion, did you take your van back to him and did he have any answers or try to make it right? I'm having him build/install a new sway bar with end links and a new track bar. The original sway bar is not doing its job and the bushings are shot. The other factor is that I'm wanting to sneak my axle forward a bit more after fitting 315's, but I'm maxed out as is with the clearance on my track bar and current sway bar, Derek already snuck it forward with his adjustable torque arms. It's an expensive project and I have been impressed with the looks and fab work that's come out of Don's shop, but I haven't talked to anyone who's had work done there and how their van drives, any insight would be appreciated.
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Old 04-10-2015, 08:30 AM   #19
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Re: Death Wobble - Possible Resolution

Quote:
Originally Posted by BajaSportsmobile
Sometimes, after repairing everything that can be repaired and replacing everything that can be replaced, Death Wobbles still exist because of design characteristics that you cannot change - then "masking" with Steering Dampers is totally acceptable.
I have tried this approach since day 1, attempting to repair, replace and improve every component so that it would not fail or at least not for a while. Now I am dialing in the alignment and I have decided that I will not sacrifice tire wear by scrubbing with "toe-out" alignment just to prevent or hide the death wobble. After this I will be looking at the radius arms. If all else fails...dual steering shocks.

Does anyone see something that I am missing? Is there something else that needs to be modified or inspected?
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Old 04-10-2015, 08:41 AM   #20
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Re: Death Wobble - Possible Resolution

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Originally Posted by REF
Sidetrack06-sorry off topic. I'm about to have Don at Boulder Offroad do some work and want to get your opinion, did you take your van back to him and did he have any answers or try to make it right? I'm having him build/install a new sway bar with end links and a new track bar. The original sway bar is not doing its job and the bushings are shot. The other factor is that I'm wanting to sneak my axle forward a bit more after fitting 315's, but I'm maxed out as is with the clearance on my track bar and current sway bar, Derek already snuck it forward with his adjustable torque arms. It's an expensive project and I have been impressed with the looks and fab work that's come out of Don's shop, but I haven't talked to anyone who's had work done there and how their van drives, any insight would be appreciated.
Don is great and has been working with me on this issue the entire time. He did the steering gearbox stabilizer bearing as well as the countless replacement of drag links and pitman arms. The reason I have it at High Country Performance right now is because I wanted to use a full size, professional alignment rack to see what is going on at all 4 corners. I have been on the phone with Don this week and he has been feeding me alignment specs for them to use at HCP. The craftsmanship at Boulder Offroad is incredible, I just happen to own a problem child. This is something I have accepted and has not stopped me from recommending dozens of people over the years to have work done at their shop. It is important to look at the size of my rig as well. I know it isn't the largest one out there but it definitely isn't small. I also do quite a bit of rock crawling that tortures the suspension and steering system. These things have probably not helped with the issues I have seen but that is one of the reasons I built this rig in the first place.
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