Projects Question about axle wiggle

That drag link is very tight. It’s actually new.the ends are not rebuilt but it’s actually all new stuff. I can’t exactly use a tie rod on my steering arm. It’s a stud

And the damper is correct. It’s mounting arm is angled,so where it’s mounted to the bones is where that angled told it to go so to speak. It doesn’t mount straight like off road trucks do,or whatever else (that’s all I can think of to compare at the moment)

 

I know it’s not your rear end because I think it’s your shitty shocks.


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Actual GM truck arms, or something else?

Most folks who say that they have truck arms actually have something quite unlike them, in both construction, and installation.

 

Read the posts again

I stated it does it with or without them,with different shocks too....I guess they aren’t all that shitty

 

What’s it matter? Doesn’t really have anything to do with it

No,gigantic actual c10 arms won’t fit under the car.

 

It has plenty to do with it. It does matter, because rigid arms, and parallel arms will have a negative effect on all of the suspension, including the front.

Rear suspension that does not properly articulate can, and will upset the front suspension.

If you are unaware of this, now you know.

You came here asking for help, to get that, you need to answer the damn question.

 

Well you see I'm trying here anyways.
That thread is almost exactly 1yr old. That must mean there's not many miles on the new rear suspension??. Did you keep the short pan hard bar???
Current Pictures of this stuff will help a lot.

 

OK, you changed one thing. did it make a difference?? DO NOT CHANGE ANYTHING ELSE YET.

 

Try Greasing the King Pins. I know this might sound crazy but it makes a Huge difference!
I had this happen with my Roadster when the king pins and bushings were less than a year old, I tried all kinds of things to get it to stop to no avail, Then one day I was talking to my buddy who has a straight axle gasser and he had experienced the same thing and said a few pumps of grease will fix her right up! Damn if it didn't!

 

I’ve seen one. Randomly ran in to a banger enthusiast meetup one day. All original 30s stuff, not hot rodded. Don’t know what the cause was, didn’t crawl over and under the guys car, but could see the death wobble hit him from 50 yards away. Wheels shaking all over the place, from even a minor crack in the road.

I’m assuming that when everything is right, factory setup works correctly, so something was worn or missing or broken.

Didn’t seem to bother him, he just puttered off down the road with the front end waggling all over the place.




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It’s a harmonics problem. Had a bad drive shaft on my OT DD once. Vibrated like crazy, but only at certain speeds.



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I had a similar shake in my Sport Coupe a some years ago. It tool a long time to find it. I could not get any of the front end components to wobble by hand when the car was jacked up. Eventually I removed the king pin cotter pins. With the cotter pins removed I could wobble the LH wheel ( our passenger side). I found that the king pin boss on the LH side of the axle was out of round. The cotter pin must have held it tight enough to mask a physical inspection. I had the axles king pin boss shrunk and then re-reamed back to standard and now all is good.
Phill.

 

Thanks for the input

If we could get a consensus that the most common cause of wobble in a stock Ford wishbone unmodified car is when parts are worn we may be more easily able to pinpoint an alteration in the front end that rodders make as the root and we only want to focus on rods where no worn part are the causation .... Obviously the most common alterations in a hot rod front being dropped axle, spring manipulation and split bones? and in my mind the split bone being the most likely choice??

Still just speculation but looks like were pointing to panhard and ideal caster as possible cures again?

 

Update,did a few things,got the bones mounted at 6* and drove it. No real noticeable change.

But I found 2 other problems. One is that my passenger front kingpin has a little play,I can see the bearing wiggle a bit when I grab the wheel. Also (very stupid) my front body bolt was t very tight. It was sort of ‘exaggerating’ the car vibrations.

The issue is still there but it’s really not all that bad now. I’m still probably going to keep working on some of the front end though just cause I’d like it to be right.

 

M A Hooligan, the notification of posts on subscribed threads dropped out on me AGAIN not long after I asked you about prior riding and wrenching on straight axle cars, before you answered that you had little prior contact with them, and I just stumbled back across the thread yesterday and read that answer.
Ford made about a jillion side steer straight axle cars without a panhard bar and I don't think that's the source of your problem, if you have a problem at all. I agree such a bar is needed with cross steer. And most of them used the ball and socket drag link which you have stated is new stuff, and I doubt that's a problem, if indeed you have a problem.
Certainly, if you find worn parts, do what's necessary to fix. But I feel that also you need to be a passenger in some other cars with straight axles, as they do drive and ride lots differently than an IFS car. You just might find that what you're concerned about is normal on a lightweight, straight axle car.
None of this is criticism, just thinking out loud

 

I will not claim to be an expert on this. Some guys here were building and driving these types of cars when I was still peddling around the driveway on a tricycle. But, as I understand the problem, Death Wobble has nothing to do with split vs. unsplit bones.

Death Wobble is defined as an uncontrolled oscillation in the steering parts of the front suspension. If you took a theoretical stock straight axle car with no DW problems, and split the bones, keeping the rest of the front end geometry to original specs, you haven’t changed anything in the steering, so should have no DW. Right? (You may have induced other problems, but let’s ignore those for right now.)

If you re-arch the spring, that alone doesn’t change the steering bits, but you also have to deal with shackle angle, and you have moved the steering bits in space in relation to the rest of the car, and each other. So could a lowered spring cause DW? I’d say no, but with the caveat that the spring change could be related to DW if it caused you to change something else that actually caused it.

Dropped axle to me seems like the spring, where just the axle change doesn’t do it, but you can’t just drop the axle, you have to rework the steering bits because you’ve moved them in space. You’ve also changed the length of a lever in the system.

DW is an oscillation. You’ve turned something in to a spring that was intended to be a solid link. You’ve allowed something to move in a way that it should not. The cure is finding the spring and turning it back in to a solid link and/or adding a shock absorber to dampen the oscillation before it gets started.

I think the preference here is to find the spring. Most commentary is around staying close to stock forms, where we know safe operation is possible, given that nothing is worn or damaged. That’s in natural conflict with the hot rodder’s urge to change things to make his car cooler looking or better performing than stock.

This place isn’t about restoring Tin Lizzies to stock specs and puttering around at 20 MPH. The further you get from Tin Lizzie specs, the cooler your car is, but the more likely you’ll run in to problems the factory cars didn’t have. We are, by nature, pushing in to the safety envelope these parts had designed in to them in ways the original designers could never have imagined. A few guys here have the engineering chops to design and fabricate a front end that will not DW. The rest of us have to rely on folk knowledge of what works, sorted out by 80+ years of experimentation and word-of-mouth history.

A panhard bar is more about bump steer, it should not change anything related to DW. Possibly the bump steer is the trigger for DW, though, so maybe adding one seems to be a cure.

A change in caster could change the starting point of oscillation, or the likelihood of the DW oscillation starting, so maybe that helps or hurts too. In splitting the bones, dropping the axle, and re-arching the spring, you’re going to be changing caster, even just to get it back to, or close to, factory spec.

One more thought, these parts are not theoretically perfect specimens. No one axle, or tie rod, is exactly the same as the others. Metallurgy wasn’t perfect then, and isn’t perfect now. Tolerances matter, and even a system that “should work” may not in the real world.

I don’t understand the dislike for dampers here. They seem a natural solution to the DW problem. Given how far from stock we’re going with some of these changes, I think you’re always going to see some DW problems without a damper. Not as a band aid on a poorly designed front suspension, but as part of a well thought out and designed system.




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Ford started using panhard rods when they went to longer, unstressed springs in an effort to soften the ride. When the springs hang on the shackles with no preload the spring can't hold the axle in place properly. Thus the need for a panhard bar on those cars.
His spring and shackles seem to have no preload as they sit right now...so resizing the main leaf or the simpler addition of a panhard bar should help.

Also...People keep assuming death wobble but what the OP is describing certainly doesn't seem like the death wobble I've experienced in two different vehicles!
I really think he would know if he ever got it. The first time I ever experienced it i just about had a heart stoppage!!!

Model A Hooligan... You keep saying your draglink isn't level.
You do realize its not supposed to be with split wishbones, correct?

With a 4 bar suspension yes...but not with split bones.
Totally different requirements between the two. It is possible to have too much angle and cause tie rod end issues for sure...but being level for the sake of level isn't what you need.
A chart has already been posted in this thread to show how and why things work as they do.

 

There ia a very clear view of the right front spring shackle in the pics on posts #&, #34, and#35, and while the angle of the shackle may be a bit steeper than 45*, it sure as hell ain't vertical, or 90*. So the spring IS IN STRESS. With side steer, the small amount of lateral movement possible with this shackle angle certainly isn't going to affect the steering, which is by longitudinal movement of the drag link.

 

Don't go raising your voice at me! Hahaha

Without even considering the amount of weight missing off his car in this picture...the shackle angle looks excessive and I don't see lateral movement being resisted much at all, especially when its being driven over humps and bumps etc.
I doubt very much that a spring spreader had to be used to connect those shackles to that spring. On my T I had to draw the spring into place with the shackle mounts. No need for a panhard there!

One other thing, he has stated multiple times that there are no steering issues with the car. The cars not darting...just wiggling in the suspension a bit...and its not being transfered into or thru the steering.

 

I think the dislike for dampers is that they weren't used "back in the day". But, I don't agree that they aren't a good thing for our hot rods. I installed one on my rather traditional sedan when I was having some "follow the groove" problems and it helped.

I think everybody will agree that German engineering has been at the top of the game since the 30's, and VW's have been using these dampers since close to then. So why can't we agree that dampers do have a valid purpose. I think the dampers sold for our hot rods is probably the exact same part that Monroe manufactures for a 1960 bug. Maybe our hot rods could be designed a touch better (like a VW bug probably could have), but in the mean time a damper might just be the hot ticket to keep us comfortably on the streets.

 

I think the issue is the rush some have to suggest their use as soon as someone says their car has death wobble or some other problem.
Many times theres no suggestion at all to first check for even the most basic stuff like a sloppy steering box or loose components.
you know...stuff that can come back and kill you when it eventually falls apart! LoL

 

Correct, it's a steering affected wobble but on a ford the steering is connected to the spindle and thus to the axle and ground.. which means if your steering is oscillating so is the axle if not secure and the more caster you have the more lateral load is put into the axle the worse the effect.. when considering when a bone is split all that's holding the axle laterally is spring, heavy load inputs threw the axle to the spring with the first oscillation causing a chain reaction..?? This seems a logical scenario when we have had accounts that reduced caster can have a positive effect.?

If it is steering induced as you describe that would mean it would stem from play/give/improper geometry in the steering links, arms or box.. a possibility but the axle more than likely especially if using un-altered ford steering arms where the geometry should be the same.....

Not necessarily related to the op's car but I still think panhard, ideal caster and no play/proper geometry in steering for d.w??

So if you have a car with caster induced wobble and can't tune it out with such a panhard MAY have some effect in a split bone car.. to many variables with the number of cars out to know to what effect in a general application... Cure? don't know but it may be easier just to build your car with one rather than trouble shoot down the road...

As for the panhard being used for bump steer the one in the rear of my A is to keep the axle located properly..

 

I’ve read this thread from the beginning and have seen many suggestions as to changing the design of the front end. Well, sometimes everything can be right or seem right and can still have a problem. I base this on experience. We received three identical fire trucks at my dept. Built inline at the factory. They had straight axles, sprung differently the the op’s axle, but still straight axles.

In a while one of the engines developed the death wobble when it hit a certain railroad track. Checked everything possible, it was exactly the same as the other two. The other two could cross that same track , no problem. All three front ends measured/ were the exactly the same.
Contacted my go to truck front end shop, an old hand told me to change to angle of the king pins and the death wobble will go away. He meant to tell me to decrease the angle I later found out. I acquired some 2 degree shims and INCREASED the angle 2 degrees. The death wobble disappeared.
Went back to thank the man for helping me, told him what I did, he said you should have decreased the angle! The problem was gone so I left that way.

My point is some times when you have front end problems on even on factory built vehicles , and everything looks right, you are force to change something.

As for the dampers, you should first eliminate your problem! Then add a damper for insurance.

Bones

 

Is the un-split wishbone providing lateral restriction on axle movement? I was thinking that it doesn’t. Only the spring and shackles are doing that.





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I wonder…..you said you have a truck arm rear suspension, how long is the panhard bar in the rear? A too short rear panhard will wiggle the car, with truck arms the panhard should attach to the frame rail and go as far to the opposite side of the axle as you can go, so it arcs very slowly and in a long arc so as not to push the car around. Maybe?

 

Interesting note on the panhard bar being added with the change in spring design. Thanks for that.

I’m not assuming anything here. But it seems that all H.A.M.B. threads that mention front suspension devolve to either bump steer or death wobble.



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I THINK so.. it forces the spring to deflect more for a given amount of movement when triangulated..

If we pinpoint death wobble and ways to cure I'd call it evolve.. sort of the point in a forum..

 

Well I'm glad to report I fixed a wobble problem with my '30 tudor. I had a bouncing problem at around 60mph so I balanced the tires, did not help, I replaced kingpins, did not help, even made it worse. Found one tire was not round so I sanded it back to round, or as round as I could. That made it worse yet. So I bought new tires, that made it a little better but not much. The thing that fixed it was correct the toe-in. somehow I had over an inch of toe-in. When I put the car together I thought I set it at 1/8" but I guess not, then I made it worse by not checking it after replacing the king pins....just goes to show you a quick check with a tape measure works wonders.

 

General comment on this DW thread, Noticed NO jam nuts on Heim joints on split Bones. This is a bad practice as the threads will wear and loosen up. This a SAFETY comment not a suggestion on eliminating wobble. Also the heim joint does not allow for too much offset movement, make sure they have the approriate sized spacers against the frame mounts, AND use large enough (outside diameter) washers on the out side of the Heim joint to prevent failure if the "ball" breaks away from the body. I like old style Ford tie rod ends as they can be greased and are pretty strong.
Make sure all cotterpins/lock nuts are used when installing components.
Hope Hooligan finds the solution & reports back

 

Everything's got to be new and tight! King pins, Wishbones must fit the axle or have to be shimed with big washers, pins and rod ends, Spring and U bolts, Steering box No Pitman arm play. and these large drop axles 4" 5" 6" all flex when you steer. Yes a steering stabilizer is good to use.Flip the steering wheel back and forth and you will easily see what's not new and loose. I have the same setup on my 29 roadster and had to change my steering box it had too much slop in it even after adjusting it for too much play.
If you switch to cross steering like 35 to 48 all the problems go away.