First Time Death Wobble

[alanack6795]

10 minutes ago, Mopar1973Man said:

The whole "Death wobble" experience thing. Why is it that people like myself gone nearly 300k miles and never had one problem with it? Stock suspension and the only thing I've got is Rancho shocks with over 100k miles on them. Then all of sudden someone gets "Death Wobble" then always seems like now that person need high dollar shocks (Bilsteins), high dollar suspension upgrade (3rd gen track bar), etc. What I'm trying to figure out what is the magic that has prevented me from ever getting the problem vs. someone like @leathermaneod that now is spending big money on trying to stop the "Death Wobble" problem.

 

This could not be more true.

 

People do not understand death wobble.  Death wobble is not the truck bouncing after hitting a pot hole. 

Death wobble is caused by excessive caster.  (Think the front wheels on a shopping cart) 

Death wobble can be caused by #1  a very worn trac bar,  bad hubs, bad ball joints.  Thats it, i've never seen bad tie rods, or steering box cause death wobble.  They can cause a shimmy, bump steer, or wander but not death wobble.

 

[leathermaneod]

Just to clarify, I don't think Bilsteins are any more than Ranchos at about $70-$80 each. I don't have any other high dollar suspension stuff, just recently replaced stuff, the tie rod upgrade, and steering box brace. Nothing else extravagant. I'm also not going to be spending any big money on trying to fix this unless it starts becoming a regular thing. As it sits, having only happened once, I will be getting my toe checked, since I never did, getting matching tires on the front, and maybe putting the damper back on. I'm not quite sure why you have had such good luck when few else do, but my guess would be two things. First is that you have owned your truck since new, and I doubt you have ever abused it. Used and worked it yes, but some people are incredibly hard on things for no good reason and I know you are not. Second is the way you meticulously maintain your vehicles. Most of us who own one of these trucks, especially young guys like me, are not so lucky as to have bought it new and took good care of it since. We are stuck fixing the issues the PO left go unresolved. Just my $.02 of course :-)

[Mopar1973Man]

https://en.wikipedia.org/wiki/Caster_angle

 

https://en.wikipedia.org/wiki/Camber_angle

 

Just some info...

[leathermaneod]

17 minutes ago, alanack6795 said:

 

This could not be more true.

 

People do not understand death wobble.  Death wobble is not the truck bouncing after hitting a pot hole. 

Death wobble is caused by excessive caster.  (Think the front wheels on a shopping cart) 

Death wobble can be caused by #1  a very worn trac bar,  bad hubs, bad ball joints.  Thats it, i've never seen bad tie rods, or steering box cause death wobble.  They can cause a shimmy, bump steer, or wander but not death wobble.

 

Whoa hold on! I though caster was supposed to be maxed out on these trucks?? I literally just got done doing the lower control arm bushings and maxing out the caster to improve my return to center. Could that be what caused this??

[Me78569]

My death wobble issues have anyways been tire related.

[Mopar1973Man]

Very possible...

[leathermaneod]

But what's the deal with the caster? Before I was told to max it out, but now @alanack6795 is saying it may cause death wobble?

[Mopar1973Man]

Try an experiment... Reset it back to where ot was roughly and then go for test drive and see what happens.  

[alanack6795]

Just now, leathermaneod said:

But what's the deal with the caster? Before I was told to max it out, but now @alanack6795 is saying it may cause death wobble?

 

I'm not really sure what you did.   bad caster, Loose Caster however you word it.  Camber can cause it as well but unless you have a loose or special adjustable ball joints its static

2 minutes ago, Me78569 said:

My death wobble issues have anyways been tire related.

 

Tires can't cause deathwobble

[dripley]

25 minutes ago, alanack6795 said:

 

This could not be more true.

 

People do not understand death wobble.  Death wobble is not the truck bouncing after hitting a pot hole. 

Death wobble is caused by excessive caster.  (Think the front wheels on a shopping cart) 

Death wobble can be caused by #1  a very worn trac bar,  bad hubs, bad ball joints.  Thats it, i've never seen bad tie rods, or steering box cause death wobble.  They can cause a shimmy, bump steer, or wander but not death wobble.

 

Are you saying excessive positive or negative camber, or either?

Back when my oe front end parts were shot I never had any DW. that was with 240 or 50k on them. Replaced everything then and still no DW until about 325k on an old set of tires. Put new ones on and it did not happen again until 380k when that last set of tires were gone. New set now and it has not happened yet. As far as caster, the adjustment bolts on mine have never been touched since new.

[leathermaneod]

26 minutes ago, alanack6795 said:

 

I'm not really sure what you did.   bad caster, Loose Caster however you word it.  Camber can cause it as well but unless you have a loose or special adjustable ball joints its static

 

Tires can't cause deathwobble

I maxed out the caster by turning the adjusters. I have the marks pointing forward. Basically making the control arms as long as possible. I thought that should still be within spec. 

27 minutes ago, Mopar1973Man said:

Try an experiment... Reset it back to where ot was roughly and then go for test drive and see what happens.  

That would be fine except I don't think I could get it to do it again. Certainly not right away, and I can't drive the same stretch of road because it's 300 miles away. As I said it's only ever done it once. Even in the 300 mile trip...the caster wasn't even the same on both sides before. I will get it checked when I get the toe checked though. 

Edited September 21, 2016 by leathermaneod

[Royal Squire]

How is shimmy different than death wobble?

[Mopar1973Man]

The one to time I was on a Goldwing motorcycle and seen death wobble start on a 2nd Gen dodge truck... The axle was violently rotating bouncing upward motion so as one side came down the other side was up off the pavement. kind of a cranking motion left to right as the axle hops. As I watch it start and the watch the driver stomp on the brakes and as the speed slows down the axle stops and back to normal driving. After seeing from my vantage angle it was a real eye opener. 

[Me78569]

A tire that is out of round can cause death wobble.  It might not be the same death wobble but I dare you to tell the diff.

[dripley]

1 hour ago, Me78569 said:

A tire that is out of round can cause death wobble.  It might not be the same death wobble but I dare you to tell the diff.

Maybe that is why the only time I have seen it was when my tires were on there last leg. Both sets were the Cooper ATP's. On my third set now. I have never felt anything weird in the steering wheel when it has happened.

[leathermaneod]

1 hour ago, Mopar1973Man said:

The one to time I was on a Goldwing motorcycle and seen death wobble start on a 2nd Gen dodge truck... The axle was violently rotating bouncing upward motion so as one side came down the other side was up off the pavement. kind of a cranking motion left to right as the axle hops. As I watch it start and the watch the driver stomp on the brakes and as the speed slows down the axle stops and back to normal driving. After seeing from my vantage angle it was a real eye opener. 

This does not sound like how my wife described what was happening on my truck. I'll have to check back with her and make sure, but she said the wheels were wobbling back and forth, as if I were turning the wheel back and forth. Not up and down I don't think.

Edited September 21, 2016 by leathermaneod

[Haggar]

Quote from tire rack's tire tech pages. 

"Increasing the amount of positive caster will increase steering effort and straight line tracking, as well as improve high speed stability and cornering effectiveness. Positive caster also increases tire lean when cornering (almost like having more negative camber) as the steering angle is increased.

What's the downside to positive caster? If the vehicle doesn't have power steering, a noticeable increase in steering effort will be felt as positive caster is increased. Other than that, the effects of positive caster are pretty much "positive," especially increasing the lean of the tire when the vehicle is cornering while returning it to a more upright position when driving straight ahead."

 

In our 4x4 trucks you almost can't get to the point of too much caster angle.   There just is not enough factory adjustment.  And "too much" just adds steering effort not controlability issues  in fact controlability is better not worse.  

 

Back to where our problems arise....  wow.  as ride height changes in bounce and rebound, the axle moves laterally, (the track bar is attached to the frame...)  depending on how far the axle is moving, caster and camber is changing (the axle housing is rotating about the instant center of the control arms...)  Toe is changing.... due to both lateral axle movement and the fact that the steering box is attached to the frame.  These are movements in a perfect world.  Add in the fact that there are loosenesses associated with each mechanical component (more when worn or loose...) and it is a nightmare of who is to blame, or is it a combination.  (I didn't bring in spring rates, tires (can be a HUGE issue, especially if they have their own spring rate that can drive the issue.) shocks and sway bar (which can change spring rates.... I noticed you mentioned it, but usually it only comes into play when turning... but Mike's description of what he saw, left/right tire fighting each other, should be damped by sway bar, not excited by it.) 

 

anyway i think i have made this just about clear as mud. 

 

HTH 

Hag

[leathermaneod]

20 minutes ago, Haggar said:

Quote from tire rack's tire tech pages. 

"Increasing the amount of positive caster will increase steering effort and straight line tracking, as well as improve high speed stability and cornering effectiveness. Positive caster also increases tire lean when cornering (almost like having more negative camber) as the steering angle is increased.

What's the downside to positive caster? If the vehicle doesn't have power steering, a noticeable increase in steering effort will be felt as positive caster is increased. Other than that, the effects of positive caster are pretty much "positive," especially increasing the lean of the tire when the vehicle is cornering while returning it to a more upright position when driving straight ahead."

 

In our 4x4 trucks you almost can't get to the point of too much caster angle.   There just is not enough factory adjustment.  And "too much" just adds steering effort not controlability issues  in fact controlability is better not worse.  

 

Back to where our problems arise....  wow.  as ride height changes in bounce and rebound, the axle moves laterally, (the track bar is attached to the frame...)  depending on how far the axle is moving, caster and camber is changing (the axle housing is rotating about the instant center of the control arms...)  Toe is changing.... due to both lateral axle movement and the fact that the steering box is attached to the frame.  These are movements in a perfect world.  Add in the fact that there are loosenesses associated with each mechanical component (more when worn or loose...) and it is a nightmare of who is to blame, or is it a combination.  (I didn't bring in spring rates, tires (can be a HUGE issue, especially if they have their own spring rate that can drive the issue.) shocks and sway bar (which can change spring rates.... I noticed you mentioned it, but usually it only comes into play when turning... but Mike's description of what he saw, left/right tire fighting each other, should be damped by sway bar, not excited by it.) 

 

anyway i think i have made this just about clear as mud. 

 

HTH 

Hag

I like your post Hag, but you didn't offer and opinion on what to check first lol

I think I am honestly leaning mostly toward my tape measure toe being off and not enough. Also maybe a combination of that, my two different tires, and lack of steering damper. Then besides all that, it may have just been a fluke. 

[dripley]

This is like shopping for ball joints. Nothing but a headache.

[rancherman]

What method did you use to  'measure'??

I  take a  couple  lengths of  angle iron,  and   a  couple of  zip ties  to hold it  snuggly against the tire.   just  slightly below  axle  CL.  ( lower if the body gets in the way)  but  away from the   bulge on the lower part of the tire.

These  angles   stick out about a foot  in front and behind the  tire. 

That gives me a nice  way to 'hook' the tape measure..     I  shoot for  a little toe in..   about  1/16- 1/8th.

Oh,  btw,  this is  with the  full weight on the  axle too.