Scary ... What the hell happened ?

Been chasing death wobble on my '98 Cherokee for a while now as well. First time it happened was at 70 on the highway.... not fun.
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Have you checked the track bar ends?
 
To stop a car from shimmying while driving you need to swing the steering wheel slowly back and forth a few times, this will usually do the trick. It can't shimmy while you're turning as you're side loading all the steering parts and taking the slack out.
 
katy said:
Have you checked the track bar ends?
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Yup, also been to a trusted shop and they were just as stumped as I was, they said everything was tight and the alignment was good. A new set of tires mostly eliminated the problem though it will still shake sometimes on a rough road, usually goes away on it's own after a few oscillations.
 
My front wheels shook at 20 mph too. I jacked up each front wheel and like John, my wheels settled at one heavy spot. I had to put 5.0 oz wheel weights on one wheel and 3 oz on the other one and that got rid of the severe wobble. There is still a come & go vibration at just under 50 mph so it is not yet perfect, but wheel balance will certainly create the death wobble.
It is easy to check by jacking each wheel just off the ground and see if it keeps settling at the same point on the wheel after you spin it.

By the way, I first put small magnets on the wheels as weights until I found the balance point and then weighed the magnets on a postal scale to come up with the snap-on wheel weight that I needed.
 
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can also happen with radial tires when a belt breaks..........


came home from NY last week in my taurus and at exactly over 50mph, car shook violently! drove the last 2 hrs home under 50 and no problem. took wheel off and tire looked like a crooked donut. rubber was all cracked in the center........
 
I also recommend looking at the front spring. Does it still have a arch to it or looks flat. A worn out spring will throw the angle off at the radius ball. The shackles can also hit the axle with a worn spring.
 
Think about it this way. If you have the slightest slack in anything in the front end, and you have zero toe in/out, then the slack can flop back and forth unblocked. If you put in a bit of toe in, that slack will be taken up when the car role forward, and with a slight pressure one way on the slack parts, they won't be flopping back and forth.

This issue is old as the hills, and toe in has always been the first thing to try in correcting it, as it takes up any slack, by putting a bit of side pressure on the parts and prevents the flop. Sure, any slack should be corrected, worn parts replaced, etc., but toe in will cover up a lot of sins of worn front end parts. It may take up to 1/4" of toe in if things are badly worn, but give it a try.
 
Good Morning all...There is a reason that many new cars have steering stabilizers and quite more sophisticated front ends then our Model 'A's have. I have used a steering stabilizer for six or seven years on a completely rebuilt front end on our 1931 Tudor. Really bad roads or railroad tracks would start the shaking. With the stabilizer, I have no repeat problems...Occasionally an after market product is an improvement! Ernie in Arizona
 
Once had a car that occasionally had a bad shimmy, couldn't find anything loose or wrong, took it to a dealer and they couldn't find anything either. I finally found that one tie rod end was very very slightly loose. replaced it and shimmy was gone.
 
Though this is not likely the case for a Model A, since others are mentioning other vehicles they've had with the problem, here's one for you. Many years ago we had a 1974 Dodge B100 van. It would get the death wable like nobody's business. Shook the entire van until you brought it down to a near stop. Replaced every stearing linkage on the thing, then finally decided to tear into the stearing box. While unbolting the box, found a crack in the frame right around the the mounting bolts. Took the stearing box out, welded up the frame and never had the problem again.
 
Thanks all, for taking the time to comment on my problem. I'm a little disappointed though. I thought it would be cut and dried ... didn't expect there to be so many possibilities. Since I'm no mechanic, it's especially problematic. I've owned the car for two years and have yet to find anyone who knows anything about model A's, let alone willing to work on one. This will be a real challenge. I've compiled a list of all the possibilities you all have suggested and have put them in order of probability. (it's a long list). I'll start working on it to the best of my ability and see how far I can get ... starting with wheel balance, then toe-in, and so on. Thanks again, guys ... I really appreciate it.


Dave
 
Thanks all, for taking the time to comment on my problem. I'm a little disappointed though. I thought it would be cut and dried ... didn't expect there to be so many possibilities. Since I'm no mechanic, it's especially problematic. I've owned the car for two years and have yet to find anyone who knows anything about model A's, let alone willing to work on one. This will be a real challenge. I've compiled a list of all the possibilities you all have suggested and have put them in order of probability. (it's a long list). I'll start working on it to the best of my ability and see how far I can get ... starting with wheel balance, then toe-in, and so on. Thanks again, guys ... I really appreciate it.


Dave
 
Dave, the first test I would do is sit someone in the parked car driver's seat and have them swing the steering wheel right and left continuously, past any slack in the steering box and far enough to load up all the steering joints, both pushing and pulling on them alternately. While this is happening look under the car at every joint and see if there is any lost motion -any slack that is.
Look at the Pitman arm to steering box connection, at every spring-loaded ball joint at the ends of the track rods and under the car at the big ball joint on the radius rods ("wishbone") under the transmission. This ball will move up and down in the socket if worn.
All this is done with the wheels on the ground and the car stationary.
Then Jack up the car and try to rock each tyre in and out vertically, top and bottom, using both hands, and then do the same thing horizontally. Have someone else look under the car while doing this to check for play in kingpins and/ or wheel bearings. It is hard for one person to rock the wheel and look inside the wheel to see where any slackness is. It is important to visually determine iif the kingpin bushes are slack or the wheel bearings are loose. Both will feel the same to the person rocking the wheel vertically. Horizontal rocking will show up any slack in the tie rod ball joints.
If nothing shows up here then look elsewhere, but this is a very simple starting examination without even getting your hands dirty. Unless your tyres are covered in mud!
SAJ in NZ
 
When I google Womelsdorf, PA, it appears that you live in a pretty small town, but that you are within driving distance from some larger places like Philly. I highly recommend you hook up with someone in a local club in one of the larger cities. I live in a town of 35,000 people and we have a pretty active club and I have benefited greatly from membership! Someone will be able to help you out and they will be only happy to do it. If you are already in a club, then disregard, but I cannot begin to express just how much I have been helped by locals.
 
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Back in 63 I had a 55 chevy convertible and was working for a Buick dealership, I developed a low speed death wobble and talked to an old timer in the front end department and he told me "boy you have a rear tire out balance". I thought no way is he right, but we ran it in after work, balanced the rear tires.problem solved. Look to simple things first.
 
A shop that works on trucks should be able to tell you what is loose, unbalanced, or out of alignment. They might not have parts to fix it but at least could balance and set proper toe in or other alignment issues.
 
A vibration by itself is generally just a pesky nuisance. When it reaches resonant frequency on major components, it can become a terrifying experience.

Helicopters can get into ground resonance which is when a rotor vibration or out of phase condition causes the landing gear structure to resonate between the aircraft and the ground. It's been known to wreck rotorcraft and the pilot's ego. It comes on in the blink of an eye and all a pilot can do it either pull it back up off the ground or chop the throttle.

Steering resonance problems happen in much the same way. A vibration in one wheel or more can start the resonance of the steering control system at a particular rpm frequency. The looser the steering control system components are the worse the resonant movement can be. This is why it will usually only start at a particular speed range but not at a higher or lower speed. Vibrations can be from a spanwise weight imbalance of the tire/wheel assembly or it can be from a phase problem due to a bent rim. Bad tires with tread or ply separation can also cause the vibration. A tire that has set and developed flat spots can do it as well.
 
Dave,in my model A club loose front radius rod ball is the number one cause of shimmy. Get under the car and shake and pull on the rod in front of the ball under the clutch housing. Easy check.

John
 
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