High Speed Vibration 72 Duster help!!!

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duster-z

duster-z

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Kansas
I have had this car for a while now thought i fixed the problem multiple times but today it just did it again.
History
- started as slant-6 car (no problems except engine blew up)
- got a donor car for suspension, 1973 dodge dart 340
- installed the 8 1/4 rearend and small block front end and replaced all ball joints and tie rod ends and what i thought was all of the rubber up front along with a used steering gear- all new tires and uni-lug rims
-car drove fine a few times on the highway then one day started the vibration i have not been able to get rid of since.
- had to get new front tires due to poor front alignment eating them
-replaced rearend with a 8 3/4 out of a challenger due to the bearings eating the axles on the 8 1/4
-vibration still there so had two different people help me change the front bearings at different times and several times re adjusted them.
- tried someone else's wheels on my car with no change
-found out that i did not change the front lower bushings and thought i finally found my problem
-replaced engine mounts with new ones as well as a new steering gear due to a leak in the used one
- got all new wheels and tires and had the car aligned by a old school guy that worked on these cars when they were new
-i thought the last three things fixed it until i drove it on the high way while it was not as bad its still bad enough i had to get off the highway

Now for a better description of the vibration it comes and goes as it wants but is only triggered by highway speeds and normally only starts after being on the highway for 5 mins. when it starts it starts in the steering wheel and then moves into the front of the car until its shacking so bad it feels like the front of the car is going to fly apart. But i can pull over on the high way stop then wait a bit get back on then the vibration is gone then i go for a bit more and it comes back. Today i got of the highway the vibration went away and the car drove 20 more miles to work at around 45 with no vibrations.

Sorry for the long post but i have not been able to figure this out for several years now and im about to the point of throwing the entire front suspension away and starting over.

Any help would be great.
 
uni-lugs rims.. are they Keystones? <- this may not matter, it is just the experience I have had. My brother-in-law had a set on a front drum brake car years ago - there is a weight on the outside/face of the drum that interferes with mounting the wheel, you'll need to get a set of spacers if this is the case.
 
ScampMike said:
uni-lugs rims.. are they Keystones? <- this may not matter, it is just the experience I have had. My brother-in-law had a set on a front drum brake car years ago - there is a weight on the outside/face of the drum that interferes with mounting the wheel, you'll need to get a set of spacers if this is the case.
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I had heard that uni-lugs have alot of problems but i am running regular wheels now with the right bolt pattern.
 
I would do a thorough inspection of ALL front end parts, and I mean everything, upper and lower ball joints, and every moving piece of the steering.. My guess is a worn out part allowing a high speed wobble.
 
limegreen70 said:
What Did you do to Blow up a Slant/6?
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Well i did it in high school i changed the spark plugs and i didn't know about the seals on the metal pieces around them and i lost oil and by the time i heard it it was to late. I got oil back in it but the engine seized the next day i went to drive it.
 
Bad Sport said:
I would do a thorough inspection of ALL front end parts, and I mean everything, upper and lower ball joints, and every moving piece of the steering.. My guess is a worn out part allowing a high speed wobble.
Click to expand...

double check ALL front end parts,strut rod bushings,uca bushings,lowers too,idler and pittman arms,wheel bearings ect.you have tried differant wheels and tires so i assume these to be ok.double check drive shaft u joints and the balance,if vibes are worse as speed increases=ujoints or balance of shaft.good luck,there are a ton of things to cause vibrations.
 
i will look at the idler arm again but i have changed it twice along with the pit-man arm.
 
Your saying comes and gos at different speeds, wheel out of balance , thats what i was told when my dart sport was doing the same , had one wheel on the back out .50 weight .And it went away .
 
have you balanced your drive shaft? are your u joints good?, is the rear end mounts in good shape-- pinion angle good? just a few more items. any unusual noise from the tranny when this is occurring?
 
On a motorcycle, we'd call that a speed-wobble. And it's usually due to the front and rear wheels not on the same centerline, or the rear is delivering a thrust angle, that is; the rear end is not centered or not adjusted correctly.
So you have a 73 A-body front track, and a Challenger rear track. Question is are the rear wheels a different backspace, to put the track back to stock, but more importantly, did your alignment guy find a thrust angle component to the rear install.
If the rear is driving the chassis at an angle, then the front alignment may be wrong. We used to call this dog-tracking, or doing the Nova-crawl.At slow speeds this is not an issue. But as speed increases, the rear starts to push the front sideways. Well the tire sidewalls don't put up with that for very long,before they start to complain. Then they stretch and relax, stretch and relax, acting like springs.Of course this leads to a wobble as the steering system can't handle that either. This usually has a narrow window of occurrence, and if you blast through it, you may not encounter it again, until some later higher speed point.
So as a test, pump your tires up to the maximum listed on the sidewall, and retest. If the problem is eased or moved to a higher speed, then this is likely what's happening. You can also have someone follow you to observe for dog-tracking. Dog tracking, if serious, must be corrected. If minor, a thrust angle alignment may be able to compensate.
You should be able to see this as wear on the front tires. there will be a feathering of the individual treads on each tire, and both will have the feathering on the same edge of the tire; either the left sides or the right sides. This is a completely different wear pattern as a toe problem. And as you can imagine, it's a rare pattern.
Now having said that, it's also possible that the alignment slipped, although that is usually accompanied by a pull.
You need to get this figured out ASAP, cuz every mile those tires turn, may bring them closer to a non-recovery state. When the sidewalls flex like that, they build a lot of heat. Tires do not survive long under that condition, before they start to separate inside. Then they leak air...forever. So you tube them and put them on the back. Where only 70% sits flat on the pavement until they wear flat again; which might not take long ,cuz they are easier to spin.
And sometimes they cup. Once a tire is cupped, it may never recover.
Don't throw the front clip away, I seriously doubt it is the source of your woes. It takes about that 5 minutes for the tires to warm up, and soften up. Cold tires are stiff and much harder to flex.Lots of A-bodies dog-track, esp the lwb Darts.I really think you will find it in the thrust angle.
 
4spdragtop said:
Does the wobble go away if you shift to neutral?
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I just found this forum and duster-z's problem is the exact one I've been having. Shifting it into neutral did nothing.

Was the problem eventually figured out?

For context, I have a '74 Duster 360.
 
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