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Projects Question about axle wiggle

Discussion in 'Traditional Hot Rods' started by model A hooligan, Aug 6, 2018.

  1. had a question, I’m running a 4” dropped axle,posies reverse eye super slider (full pack) steering dampener on split bones.
    Have had my wheels balanced to a T. They roll laser smooth. Until I hit a bump.

    This car has always done this, when I hit. Bump,the car wiggles. It feels like it’s almost the body,but I can see the engine shake too. Nothing is loose,and I do NOT notice it in the steering wheel. It does NOT affect my steering, but it’s a pretty violent wiggle.

    I’m wondering do I need a panhard bar? It’s not the tires or wheels. I’ve had 4 different sets of tires and wheels and it has done the same. Wheel bearings are tight,steering wheel does not wiggle.the steering is not affected at all. I’m wondering if it’s movement in the shackles

    Again, wheels are balanced nicely, I do have front shocks (it does it with or without them) I have steering stabilizer,and my steering wheel is not affected.has hidden disc brakes with good bearings (did it when I had drums also) traditional side steer f1 box. I don’t think it’s ‘bump steer’ as my steering wheel doesn’t wiggle or seem affected. And I have around 8 degrees of axle layback or caster if you will
    Last edited: Aug 6, 2018
  2. junkman8888
    Joined: Jan 28, 2009
    Posts: 393


    In order for us to help you we need pictures. In the absence of pictures, my recommendation is to jack up the car to get the weight off the front wheels, lock the steering wheel down so it can't turn, then put on the man pants and tug those front wheels in every direction, left-right and up-down, then let us know what you find.
  3. The front end seems really right. There’s really hardly any play in anything.

    I dont have pics but would be very hard to see, it’s extremely low with a flat crossmember. but it still did this with the original crossmember. Basically I’ve changed things except the bones/spring and perch and it has done this from day one.

    After hitting the bump (I notice tar snacks really do it) it will wiggle,feels as if the car is wiggling left to right (but not moving in the lane, it’s more of a shake and goes away on smooth road. It’s not death wobble or anything like that either. Feels like the car shakes but steering is not.

    I’ve redone a new truck arm rear suspension and I’m certain it’s the front that does it. The rear feels fine.It mostly feels like a crappy ride not really any thing scary about the steering.the spring shackles look like they have the right angle also.And to add,it was taller before,and did the same thing. Lowering it did not change any feeling.the car has had many changes and it’s always done this. I’ve lived with it just think it’s a old car but I’m hearing a lot of guys saying their hotrods drive/ride just fine and it’s got me wanting to fix this
    Last edited: Aug 6, 2018
  4. squirrel
    Joined: Sep 23, 2004
    Posts: 41,067


    bump steer is when the steering wheel stays still, but the act of the suspension moving up or down, turns the wheels.

    Show us a picture, side view, of front end, so we can see where the drag link is relative to the radius rods.
    trollst likes this.
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  5. trollst
    Joined: Jan 27, 2012
    Posts: 1,306


    You've given us no description of how your car is set up, we need pics, it's the only way we can see where the problems are. Is it the kind that won't meet the forum guidelines? (rr?)
  6. As I mentioned,the car does not have the steering affected, it stays In it’s lane, it doesn’t do anything scary as far as steering. It doesn’t fart from side to side or turn itself at all.

    My drag link is angled down a bit at the box. But there’s nothing I can do about it. My steering arm is dropped as far as it will go,and my box is mounted as high as it can go without hitting a spark plug.

    Pretty sure if the drag link was having issues it would move the steering wheel a bit. I literally feel none of it it in the steering wheel. The car goes straight and steers fine,just feels like the axle is doing something goofy as I can see my front window wiggling in a left to right motion it feels like. Hard to explain this.When it happens,the car does not steer erratically or anything. It pretty much feels like normal. It literally feels like the front of the body is not bolted down. (Obviously it is) I even can watch the tires as it does it and I don’t really see them doing anything. Though during the shaking everything is moving including me making it hard to focus
    Last edited: Aug 7, 2018
  7. Only pic I have that you can kinda see the front end. But it does NOT have those shocks or mounts anymore.

    Attached Files:

  8. I’ve listed everything how it’s set up I thought?
    Obviously it meets the guidelines. Ive been here probably 10 years. It’s 11pm and my car is outside in the dark..i don’t keep pics of the front suspension on my phone.
    Last edited: Aug 7, 2018
  9. Gasolinefed
    Joined: Apr 17, 2018
    Posts: 93

    from OR

    Just visualizing as I haven't tested but when you split the wishbone you un-triangulate the front end making it easier for the axle to move laterally or side to side in the frame.. so a panhard MAY be the cure??

    Built both my 29 and 31 with buggy spring, cross steer, split bone and panhards and never had an issue..

    My theory as I haven't thoroughly researched but that may be a source of some of the death wobble also.. split bone/hairpin plus cross steer minus a panhard, the only thing holding the axle in the chassis laterally at that point is a spring....
  10. martnet'34
    Joined: Jul 21, 2011
    Posts: 1


    watching intently as i also have what you describe, the feeling after hitting a small bump the front of the car shakes in a left/right kind of way, mine happens just above 60mph and seems to smooth out if i drop below 58ish mph,
  11. I don’t have ‘death wobble’ I’m pretty sure. My understanding is that is the axle moving violently that there’s no steering control until you slow down to stop it. That does not happen.

    Yes the only thing holding it laterally is the spring. My understanding is if the shackles are at 45 degrees and have preload that it keeps it centered. But obviously If i knew,It all wouldn’t have the problem

  12. Yep, if I slow down it seems to help. Sounds very similar.

    If I’m hauling ass it seems like it don’t do it.i thought it was tired/wheels but I’ve had many different sets and balanced them all very good and nothing changed. oes yours affect steering? Or not really?
  13. gimpyshotrods
    Joined: May 20, 2009
    Posts: 15,561


    Death wobble.

    You should have zero detectable play in the suspension and steering.

    If you have any, find it and fix it.

  14. Yeah.. that’s what we are trying to figure out. I’m not asking questions just to not fix it.

    I’m pretty sure it had death wobble with a set of separated tires. That was a totally different thing. As I mentioned, I understood that death wobble is when the front end has violent movement and your steering input does not steer the car at that in no steering dampener. Which I do have

    When my problem happens,I have complete steering as i normally would. It has no affect on the steeeing. It’s even done it in a corner and I could steer fine.
  15. I should add before someone asks, I’ve had the drive shaft balanced. It is definitely happening when I hit a bump
  16. gimpyshotrods
    Joined: May 20, 2009
    Posts: 15,561


    Your understanding of death wobble is not correct.

    You can still steer.
  17. I wonder what it was then when my car couldn’t. I’ve seen some vids of jeeps death wobble. Their tires are moving back and fourth violently. I can see mine,and they don’t appear to be doing that. Unless mine just is doing it so slight that I can’t see it?? I’m not saying your wrong,just really don’t seem like it would be if the steering wheel has zero feedback.others that follow me say that they don’t see the car doing anything funny at all. I’ll add that my stabilizer is clamped to my tie rod,and is connected to my passenger wishbone.

    I thought it was called death wobble cause it was scary/dangerous. When my car does this it’s really not scary. Just annoying I guess.

    I’ll try to post pics when I have them
    Last edited: Aug 7, 2018
  18. How does it act without the dampener? Better, worse, the same?
  19. Good question, I have had it in for 7 years. I only drove the car briefly without it. From what I remember when I did not have it,the wheels didn’t return to center out of a turn when you let the wheel go,and the steering was waaaay to easy/responsive. I think the car still did the same wobble though. I had other issues preventing me from going on the highway that I fixed around the same time I added the stabilizer,if I remember correctly without the stabilizer the steering wheel had some feedback.
  20. I do have a speedway tie rod. I’ve seen a member her mention his flexed a bit. Maybe I need to get a extra hand and try to force the wheels together or apart and see if it flexes. I can’t imagine anything flexing as much as the car is wiggling though.. who knows

    Also I do have a small amount of toe in.One fellow mentioned that a slight toe in could cause tension on the tie rod almost making it like a spring that will try and give the wheel feedback to point back out,causing oscillation

    I was under the impression a bit of toe in was good. I think I’ve tried zero toe with same results but I’m not positive. Maybe I can try it again
    Last edited: Aug 7, 2018
  21. mgtstumpy
    Joined: Jul 20, 2006
    Posts: 6,338


    What steering box; push pull, cowl or cross steer? Splitting and remounting wishbones out wide could impact on geometry.
    Is the steering on the correct axis, tube or I-beam? What diameter tubing for steering arm and drag link? How much caster is there?
  22. I’ve answered a lot of what you asked. I mentioned it’s side steer f1. And that I’m around 8 degrees of caster. I’ll have to double check it.

    I beam.. a tube axle doesn’t belong in my opinion.

    Many hotrods split their bones out to the frame rails.
  23. Happydaze
    Joined: Aug 21, 2009
    Posts: 664


    I'm not clear as to what the symptoms are. Does it wiggle momentarily or is it something that continues until something changes, eg reduce speed etc. I suspect the latter and that being the case the bump is setting off some kind of harmonic (albeit perhaps only rather mild). Like a flexing tie rod as mentioned.

    My 32 when acquired had a dreadful shake at about 60mph that I simply couldn't power through (or didn't have the balls to push through it), it turned out to be chronic spring bind which I discovered when trying to reassemble after an exploration. Those rather horrible self aligning spring perches fixed it instantly. Yeah I need to alter the crossmember but I've enjoyed it as it is for pushing 30 years now.

  24. BJR
    Joined: Mar 11, 2005
    Posts: 4,889


    If you jump up and down on the front frame or bumper does the steering wheel move side to side? If so you have bump steer. With a 4" drop axle you have a lot of leverage from the steering arm, trying to push the top of the axle forward and backward, kind of pivoting on the I beam. With the car parked have someone turn the steering wheel, and watch the top of the axle on the drivers side to see if it moves forward or rearward.
    Nailhead A-V8 likes this.
  25. dana barlow
    Joined: May 30, 2006
    Posts: 3,219

    dana barlow
    from Miami Fla.

    You have not added enough pics for others to really help. Your only poor pic shows front spring shackels that are not fully loaded yet with the rest of cars front lbs. =when they get full load,they will be down too far{not at 45*} =that if shackels are now hanging lower then 45* and front axle has no panhard bar it will shake/so also if rear axle set up same way with out a panhard bar. More pic's could show other probs as well. To those that can see things you don't know about an there for can't see,it's why those that wish to help ask for photos.
    Last edited: Aug 7, 2018
    Nailhead A-V8, trollst and pitman like this.
  26. Boneyard51
    Joined: Dec 10, 2017
    Posts: 1,673


    8 degrees of caster seems like a lot to me.

    Montana1 likes this.
  27. pitman
    Joined: May 14, 2006
    Posts: 4,482

    from Hampsha

    Agree, Dana. With more load the shackles angle down toward oscillation. Panhard would help, or spring length-recurve.
    Last edited: Aug 7, 2018
  28. 42˚18'N 83˚09'W
    Joined: Jul 29, 2008
    Posts: 97

    42˚18'N 83˚09'W

    IMHO. This does not sound like a bump steer condition but I would check that first. When you split the bones the front axle is then hanging only from the spring shackles. This will allow the axle to swing freely side to side as far as the shackles will allow. The shackles should be at 45 degrees at rest as Dana previously noted. A Panhard bar deletes and side to side movement which is what you appear to be describing. 5-7 degrees of caster is what I usually run (closer to 5 degrees) but 8 degrees wouldn't cause this condition. A bad set of tires can also create weird drivability issues. Good luck. When they're not right they are a PITA to drive as well as dangerous.
  29. It did it with 5 degrees too
  30. It doesnt

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