Death wobble (1 Viewer)

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kidglove13

kidglove13

Joined
Feb 25, 2009
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Location
Richmond, VA
Well I got some mean death wobble yesterday
I know the bias irok don't help abut never had it like this before
Got under the truck and did some checking
Heim joint on adjustable panhard has a slight bit of play
Radius arm bushins at the axle, 3 of the four bushings the inner metal sleeve has separated from the bushings:doh:
The bushings are original at 200k
I am going to assume and hope that these bushings and loose Heim joint are the cause of the problem
Comments?
 
Castor has been corrected with plates since the lift has been on the truck
Never had death wobble until yesterday
 
Don't know off hand but the castor is set up to properly run a DC shaft
I doubt that caster is the issue here lift and castor plates have been on the truck for over year never had an issue until now and the discovery of bad bushings and loose rod end
Toe might be a little off and I mean a little, never had an issue
Everything in the front end is new and to spec except control arm bushings and panhard Heim joint
Like I said caster has been the same for over a year so if it did not cause the issue before it is not the cause of the problem now
 
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Ok. Your wobble is caused by caster. Whether its the worn bushes or other causing it is the question. Usually with some play in panhard will cause it suddenly swerving left or right and the driver constantly correcting. The dc shaft and caster are 2 different things. I doubt anyone is silly enough to run caster out just to make the dc shaft angles line up correctly. What size lift and what brand/degree caster plates?
 
Please tell me how castor would cause the problem now and it did not for the prior year or more before now?
It is an Ironman 6 inch lift with their appropriate castor plates for the lift
 
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Alot of the time it starts out as wondering and then finally death wobble as the bushes/tierods wear in. Once it starts its hard to fix. I think it's best you get a wheel alignment and caster numbers.
 
kidglove13 said:
Don't know off hand but the castor is set up to properly run a DC shaft
I doubt that caster is the issue here lift and castor plates have been on the truck for over year never had an issue until now and the discovery of bad bushings and loose rod end
Toe might be a little off and I mean a little, never had an issue
Everything in the front end is new and to spec except control arm bushings and panhard Heim joint
Like I said caster has been the same for over a year so if it did not cause the issue before it is not the cause of the problem now
Click to expand...



Just saw you edited this post. And not to get anyone into trouble. But I doubt anyone has checked your caster at all. It won't be in spec. 5 degree caster plates give 8.8' of caster correction (or supposed to). Spec is +3'. I always aim for +3.5. Given this caster plates are only good at 4.5" of lift. Every " above or below = 1.76' of caster correction. At a true 6" of lift your caster will be around +1' (with new bushes). Warn out bushes and you could be way out. People have had death wobbles at +2'.


The ironman caster plate numbers are foobar. They say its good for upto 7" max. But you can't correct caster as the arms foul the track bar. After market replacement arms are the only option. 7" with their caster plates = -0.5'
 
I would have to agree with TheBigBoy here. There are no caster plates that can correct for 6" of lift. With new / good components the effects of the bad caster is not as obvious and is effective "masked". As parts wear, you get worse and worse handling, until you end up where you are now.

Once you start fixing things, you might get back to the condition where the driving is acceptable. Large bias ply tires are not going to help either.
 
Anyone know if it's a line you can trace .. which it's the max caster correction you can archive with plates before your tie rod tart touching your control arms .. ?

I know lift it's a mayor variable here .. just wonder if can be isolated just based in axle housing rotation given plates correction.
 
Tapage said:
Anyone know if it's a line you can trace .. which it's the max caster correction you can archive with plates before your tie rod tart touching your control arms .. ?

I know lift it's a mayor variable here .. just wonder if can be isolated just based in axle housing rotation given plates correction.
Click to expand...

From my experience the max is around 7*. I've gone as far as dropping the arms some to avoid the tie rod from hitting the top of the arms at 7* but then you are faced with the tie rod hitting the arms behind the rear bushing if you add much more rotation.

Realistically plates are a 4" solution and more lift requires arms.

or you could add drop brackets to make up the difference.
 
Worn out bushings on the control arms and panhard may be "allowing" the death wobble, which may well be caused by marginal caster settings. A worn out steering stabilizer may also contribute. None of these usually happen overnight, though. Another problem I have seen on a friend's rig is a crack in the upper panhard bracket, right where it is welded to the frame. Access is somewhat limited by the steering box. We have cleaned it up and re-welded it, and we are planning on fabbing up a larger support bracket to go from top of frame to bottom of bracket and weld/bolt in between the frame and steering box. I'm thinking 3/16 should be equal to or heavier than the original metal. A search should find other threads on this subject.
I would inspect for the crack, repair as needed, and replace the bad bushings since they are toast anyway. See if that takes care of the problem, and then decide if/when/how to deal with caster issues. John
 
Tapage said:
Anyone know if it's a line you can trace .. which it's the max caster correction you can archive with plates before your tie rod tart touching your control arms .. ?

I know lift it's a mayor variable here .. just wonder if can be isolated just based in axle housing rotation given plates correction.
Click to expand...

The 5' caster plates are max before grinding the arm down as to not rub on the track bar. Don't forget during flex it will deflect the arm upwards and closer to the track bar on 1 side. This is why I modify and build custom housings.
 
sleeoffroad said:
I would have to agree with TheBigBoy here. There are no caster plates that can correct for 6" of lift. With new / good components the effects of the bad caster is not as obvious and is effective "masked". As parts wear, you get worse and worse handling, until you end up where you are now.

Once you start fixing things, you might get back to the condition where the driving is acceptable. Large bias ply tires are not going to help either.
Click to expand...

Thanks Christo, would you believe 95% of the suspension companies here either know and don't care/or don't bother checking things for themselves and just copy other companies leads. They keep fitting incorrect caster and suspension design/solutions. And I keep having to fix angry customers rigs with death wobble. Superior engineering is the only company I've found to even have the correct caster with their aftermarket arms. All the others are out.
 
Ok, so I take the truck and get a castor sweep done to find out where the castor currently sits at.
Then I can either
A: Use castor bushings to make up the difference
B: Use drop brackets at the chassis mounts

I know that the large bias tires do not help the problem but that is what it is, I am looking to get into some radials at some point down the road.

My question is this, if I correct the castor closer back towards stock that will put the drive shaft in a steep broke back position, how will this affect the drive shaft?

Right now the pinion points almost straight at the tcase.

New arms for the correct castor correction are out of the budget

What do others who run 6 inch lifts do?

Thanks
 
Due to how bad your bushes are. I would say your caster is way out, in the negative range. Caster bushes aswell as plates is not an option as the arms will hit the track bar. The drop box's at the chassi end is the cheapest and best option. Providing it is a true 6" of lift. 2" drop box's and caster plates with new bushes will do the trick. IF your caster after this is to great (higher than +3.5'). You can buy small coil spacers to dial it in perfect. I would put new bushes in and then get caster check.

If aftermarket arms are out of the budget. You can always cut and rotate the ball ends.

As for drive shaft angles. Not much you can do. Caster is by far more important. Buy a part time kit to eliminate vibrations.
 
Do you mean the arms will hit the tie rod behind the axle?

As I already had to grind the arms to help with contact already
 
Just throw new bushes in it for now, and replace what ever else is needed. Save your $$$ and do it right when budget allows. Hopefully Socal has these housings sorted for a direct replacement that fixes all your problems.
 
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