Need diagnostic help on SEVERE steering wheel shake

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Originally Posted by R Pope

First, check the balance of the rear tires, they can sometimes set up a shake that transfers to the front end.
Are all four tires the same make? Some brands are just incompatible.
The new front bushings on the inner A-frame ends, are they Ford or aftermarket? Some are too soft, allowing movement. Then again, some are too hard, causing flex somewhere else.
Finally, get a buddy to drive beside you and watch what's happening when it shakes.

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All wheels balanced on Friday (Dynamic)
BFG rear, Goodyear front (but same problem occurred with BFG rear/Continentals front)
Inner A-Frame ends original Ford
Good idea about a buddy, doing that tomorrow morning... will try and have a video done as well...

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Originally Posted by Dave Severson

Did you check the brake rotors for cracks or warpage? Could be as simple as a wrong sized, loose or worn wheel bearing.... Another possiblity that comes to mind is the center hole on the wheel, is it large enough to fit over the hub correctly and not hold it away from the mounting surface of the brake rotor?

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Good idea, didn't check the rotors yet... or the wheel bearings... center hole looks okay... will pull the rotors tomorrow afternoon and check

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Originally Posted by jerry clayton

"20 years ago"

I have over the years repeatedly had occurrances where brake rotors have cracked at the parting line in the inner fins---causing a very violent wobble feeling as when they do start separating the rate increases and the wobble gets worse

You can check the disc thickness with a mike of dial caliper and if this is the case it will be easily measured---new discs are the only fix

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I'll have to see if I can borrow a dial caliper, not something in my tool box... I was thinking about replacing the stock discs with something larger, maybe the Wildwood set-up, This might be a good excuse to do it sooner rather than later...

Any-thoughts on whether there could be a problem in the steering column or rack/pinion?

Sure sounds like something is loose or worn badly. Have someone rock the steering wheel back and forth while you look for slack in tie rod ends,etc. Also jack each front tire up at lower control arm just enough to get a long bar under center of tire and pry up to check for worn ball joints. While tire is jacked up, grab tire at top and bottom and try to rock tire/wheel on spindle. Several places where you can find slack there (bearings, upper ball joint, rotor). Might not hurt to check for cracked weld on strg rack mounts. You need to find the problem and fix asap! You need positive caster in both sides and don't need excessive toe out. Zero toe or toe in needed. Let us know what you find.

Is this power or manual rack & pinion steering? Had a buddy in the army way back when that had an old Honda car with power rack & pinion, some internal seal or O-rings gave out and because of the internal leak from the high pressure to return side inside the rack assembly, the steering wheel on his car would do a weird toggling wobble without actually affecting the direction the wheels were pointed.

I agree with a post already here..............caster will and can allow this to happen. You do need to check it..........3-4 degrees is what you want , especially at highway speeds.

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Originally Posted by Lord Antagonism

Is this power or manual rack & pinion steering? Had a buddy in the army way back when that had an old Honda car with power rack & pinion, some internal seal or O-rings gave out and because of the internal leak from the high pressure to return side inside the rack assembly, the steering wheel on his car would do a weird toggling wobble without actually affecting the direction the wheels were pointed.

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Manual, but a good thought

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Originally Posted by sunsetdart

I agree with a post already here..............caster will and can allow this to happen. You do need to check it..........3-4 degrees is what you want , especially at highway speeds.

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Asked a buddy of mine who works at a Firestone shop to look it over with me for a third (or fourth) opinion, this morning. He's convinced that the problem is still related to miss-balanced wheels. He pointed out that the stick-on weights were all on the inside, which is cosmetically pleasing, but that due to the wheel size, etc., it would have been very difficult to balance it correctly that way... he'll take the wheels on Monday to his shop and check the balancing, just to be certain that's not the problem... if it still is, I'll start pulling tie rods, etc., next weekend. Then look at replacing calipers, (might as well put the larger brakes on now).

OK

while you have the wheels off---look at the rotors very closely---I have had split ones that you could squeese with a set of channel-lock pliers and see the movement /cracked area---

also toward some comments----a loose steering column will not cause front end shimmy/wobble---something is not in the correct specs/geometry---

Are your front wheels / hubs giving you the correct scrub radius???

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Originally Posted by jerry clayton

OK

while you have the wheels off---look at the rotors very closely---I have had split ones that you could squeese with a set of channel-lock pliers and see the movement /cracked area---

also toward some comments----a loose steering column will not cause front end shimmy/wobble---something is not in the correct specs/geometry---

Are your front wheels / hubs giving you the correct scrub radius???

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Will do,... how would I find out what the correct "scrub radius" for my set up should be?

One thing to remember is that you probably can’t use the alignment specs from the original car the front end items came from. Your car is now heaver and the weight distribution is different.

I am thinking that your caster and camber is probably too close to “O” or the combination of the two does not match what your car needs.

Take your car to an alignment shop that specializes in hot rods or custom cars. Your local tire shop and part houses only know one thing anymore (check the book and/or do what the computer says to do).

Good luck and hope you get it fixed soon.

Bug

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Originally Posted by Bug

One thing to remember is that you probably can’t use the alignment specs from the original car the front end items came from. Your car is now heaver and the weight distribution is different.

I am thinking that your caster and camber is probably too close to “O” or the combination of the two does not match what your car needs.

Take your car to an alignment shop that specializes in hot rods or custom cars. Your local tire shop and part houses only know one thing anymore (check the book and/or do what the computer says to so).

Good luck and hope you get it fixed soon.

Bug

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Good advice! Thanks!

I'm almost certain you need more caster and possibly more toe in.
If you have the strut rods you wil probably find there is a bit of bind at the "up" travel limit. My car is pretty low in front and I get just a little bind at the "up" travel limit.

I run about 7 deg caster and 1/8 toe in measured at the tire center line. About 1 deg neg camber (top of tire is closer to the center of the car.) Other than the car is a bit heavy on the steering for a light weight car it tracks very well and is rock steady in the cross winds. It actually handles pretty well for a big tires, little tires car. I did a funny car high speed back up just to relive the old days and it does ok there too. Often lots of caster would cause death wobble backing up.

Death wobble usually occurs when the alignments are very close to "0".

I have an adjustable strut rod with spherical bearings for my MII based front end suspension. No binding through the whole travel range.

Bug

if I may....
I not have as much experience with hotrod engines and old cars as you guys.
But the "death wobble" I am very familiar with.

this was very common with F350's with the Dana 60 front axle (I've owned 4 of them, and only one didn't have the problem).
The first time we had the problem we changed out EVERYTHING on the front end.
We discovered and subsequently proved that you needed a good trac bar, with good bushings to keep the axle from wobbling (which starts the movement at 45-50mph).
Also installing a good power steering dampner was essential.

I don't know if this will apply to you, but I figured I'd mention it as we've spent many a night scratching our heads to figure out the problem.

Drew