My AV8 coupe which is nearly identical to yours (blue one at Jim Linders Spamarama last year) had the same thing even with a damper that was on it when I got it. I could still barely feel the wobble. I fixed it by adding more pos caster Im actually running 8.2* and it not only fixed the wobble and I threw the damper away but it made it drive alot nicer at highway speeds the downside is it slightly increased steering effort. I also runn 22 PSI in front tires and 20 PSI in rears. Im cant remember what you have for front wishbones so adjusting them may be a big deal I had to make a decent pie cut in mine to get it where its at now. If you have hairpins that you can adjust Id at least try more caster to rule that out.
Flathead31coupe, I can tell you that the fix for the death wobble in a Jeep I had here was the factory panhard bar. It would go into wobble at times and would not stop no matter if you hit the gas or the brakes or whatever. You would pull over to a stop and then resume and it would go away. I did enough searching around the Jeep boards and it was suggested to get a new panhard. Fixed instantly, much to my surprise and delight. Now that said, I don't think you need one. Many of our cars have no panhard bars. Hell, I ran my buggy spring suicide mounted, spring mounts in the bones with no front shocks and bias plies for 3 years at top speed all over the NJ area with no wobble. 7 degrees of caster on 1940 wheel bearings and a stock a axle. I did have new king pins and bushings and new tie rod ends. I'm betting you have either a tie rod end issue or as someone else stated a tie rod that is flexing or something. I make my tie rods from .156 wall 7/8" 4130 tubing. Have a good look at yours and see what kind of material and wall you have. I've seen them made from black pipe (yikes) so look carefully. check the drag link for the same issues. And check those ends at different angles. Maybe they are worn funny and only get loose as the one corner dips? I've seen plenty of ends like that. Difficult to check by yourself so have a buddy shake the wheel with weight on the tires as well as with the car jacked up. Sounds like you went through everything else so start swapping ends. If you still have wobble at least you are eliminating something. Have to start doing that sooner or later.
A length of 3/4 angle and a handfull of hose clamps on your tierod could would stiffin it up enough to find out if thats the cause.
Gee Dick, Maybe you should have taped your lecture on "Death Wobble" that you gave at the street rod nationals in Louisville so you can charge people to repeat yourself. They might pay more attention. might be Aliens.....
dont know if it helps or not, but this issue has been there from the start, i havnt been able to drive it very far or at the speed limit sence it was built, i cant wait to get in and drive the wheels off this
Just hit mw this am. Did you look at the spring centering pin? Is it fairly snug in the x-member? That is your side to side locator.
Your problem is flex in the steering box mounting, aggravated by the offset bend in your pitman arm. The S shaped Pitman arm is allowing some flex on its own, but the offset of the arm combined with the unsupported plate style mounting of the box being well inboard of the pitman arm attachment and frame, is allowing flex of the entire box. This is aggravated even further by the removal of the mast jacket and the use of a U joint in your column shaft. The steering box is for all intents floating and has no real structural stiffness. A tubular clamp around the snout of the box and welded or bolted solidly to the frame would help...as would increased bracing of the box mounting bracket. On HAMBAndys car fitzee and I actually machined off the flange on a too wide "big car" box and ran the long box snout thru a very tight fitting tube welded into the frame rail. The snout passes thru the outside of the rail. The tube also has a pinch bolt up thru the bottom of the frame for tightness and the actual mount itself is fabricated off the 4 box adjuster cap bolts which were replaced with longer grade 8's. Very tight and no flex is possible even with the unusually long snout. You can't mount a steering box too securely.
Bill you got all that from the picture on the first page!! Your eyes are better then mine to pick up on that. You might be on to something.Would love to see better pictures on how the box is mounted.
i had the same wobble issue with the cowl setup i started with at first, then changed it to the setup i have now, didnt help...the box is mounted to a plate wleded inside the frame and has angle piece, welded to the top of the plate to the frame as well....you can jack the whole side of the car up by that bracket...very well built.
Steering box thing is valid to investigate. More pix. of the bracket? Also just looking at the steering arms and was thinking. The tie rods originally drop into them from the top right? Seeing yours I have to ask, did you ream them with a 7 degree reamer to get them to seat in from the bottom? Or are they straight drilled a bit oversized to get them in enough to get the nut on. Thinking if they weren't tapered the tie rod stud could be flipping left and right under heavy loads and causing a slip-stick motion. Maybe you will see some marks on the tops from the nut sliding around? That might give you a feeling of loose tie rod ends even if they are new. Maybe crazy but thinking inside the box hasn't gotten results so..... Also when you bend the arms down they should be bent back up at the very ends again to the same angle as when they started. In that last pic. they look a bit dropped to the rear. That would make them not parallel to the ground as they should be. Also they should be evenly done left and right. And bent at the same points so they are the same height from the ground.
Yes! That did it for me! My track roadster did the same thing until I installed a steering damper!!!!
I know, I know!!!!!!!! Loose lugs on the expressway! Has to be. Or maybe coming home drunk at 4am and the wife waiting for you with a rolling pin.
the tie rods only go in that way, they taper big to small going up....the arms are bent identical to each other....not sure being at an angle or parallel, would matter the arms dont know the difference,but i dont know.
Just so you know, I am not trying to be critical.in any way..I DIG that you are driving your car!!! WAY cool, brother!
Looks to me like your drag link is far shorter than your wishbone, giving you a bump steer problem. You might try this, if I can explain it. Jack up the front of your car and place on jack stands (fairly high too). Place a floor jack under each tire. Clamp some sort of reference pointer onto the frame and pointing at the position of the pitman arm.Tie off or lock the steering wheel. Jack one tire up and leave the other down, not pitman arm location. Now jack the other tire up and let the first one down and note location of pitman arm. You may need to tape some yard sticks to the tires to reference straight as well. Changes in pitman arm location indicate worn steering gear. Now unlock the steering wheel and do it again. Changes in itman arm location would indicate the bumps are causing a steering change in the system. Good luck Also, axle caster was not designed to be changed in solid axles by adjusting the radius rods or four bars. Axles were supposed to be bent to change this measurement. The Axle should be in a straight line with the spring/mount to prevent binding from poor geometry. If your axle caster was set by welding your wishbones you might have an axle that is binding when the spring is flexing.
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