violent vibrations

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64physhy

64physhy

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I'm posting this in this section because I'm pretty sure it's not engine or drivetrain related. At about 60 or 70 MPH, my whole car starts shaking violently. It just started after I replaced the UCA bushings, adjusted the torsion bars a little stiffer, and put on Competition engineering shocks. Because of how badly it shakes, I can't tell which corner it's coming from. Do I just need to get an alignment, or could it be something more?

Also, while adjusting the torsion bars, I noticed that the driver side needs to be tightened way more than the passenger side to achieve the same height and firmness. What would cause that?
 
Adjusting the t-bars changes the ride height and the alignment. Putting in new bushings also affects the alignment. You should get it realigned
 
doe's it stop after a certain speed ? mine shakes like mad at58- 60 but smooths back out at 64-66 , could be a bad tire ,I once bought a set of recaps { i know but I was young with a young family} that shimmied at 55 but went smooth as glass at 63 ,I know it was the tires because it started immediately after they went on and I had them rebalanced twice to try and fix it then just didn't drive 55-60 anymore .
 
I say your tires are out of balance. It needs aligned after everything you did anyway. Might as well do it all.
 
I don't think it's the tires. It didn't shake like this before. It's probably from the bushings and adjusting the t-bars. Before I do an alignment, I'd like to figure out why the adjustment is so much different on the torsion bars. It's like one (or both) weren't installed right and is rotated a notch or something.
 
Is the shake all in the body and the seat of your pants or in the steering wheel? That might help you pinpoint it some. I had a very strange similar issue with my car that I finally got more or less sorted out for the time being. My driveshaft looked off-center at the diff u joint, but I just put brand new u joints in it, so I knew that couldn't be the issue. Turns out the pinion yoke was worn more on one side of the u joint girdle than the other, letting the driveshaft wobble back and forth just a little bit. It looked like a bad u joint from under the car, but if you looked really close you could see the whole u joint cap was moving in the yoke.
 
Map63Vette said:
Is the shake all in the body and the seat of your pants or in the steering wheel? That might help you pinpoint it some. I had a very strange similar issue with my car that I finally got more or less sorted out for the time being. My driveshaft looked off-center at the diff u joint, but I just put brand new u joints in it, so I knew that couldn't be the issue. Turns out the pinion yoke was worn more on one side of the u joint girdle than the other, letting the driveshaft wobble back and forth just a little bit. It looked like a bad u joint from under the car, but if you looked really close you could see the whole u joint cap was moving in the yoke.
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It was the whole car, not through the steering wheel. I'll check out the girdles on the u-joints, that's a possibility, but the u-joints themselves are new. I have those billet girdles on the back, so I'll start there. Thank you.
 
I just found out the LCA bushings are toast. I should have changed them when I did the uppers, but the kit didn't come with them. I Picked up a set I'll be putting in tonight or tomorrow.
I checked the u-joint caps yesterday and there's no play there, so maybe this will be it.
 
I changed the bushings. The left torsion bar still needs to be tightened all the way down with the passenger side only tightened about halfway just to get the specified ride height.
I made sure the LCA was as low as it would go, and the adjustment blade was as low as it could go, too when I put the torsion bars back in. I think it was even worse after changing the bushings because I couldn't even get it adjusted to spec ride height. Either there's something wrong with the driver side torsion bar, or somebody before me installed them on the wrong sides or something. What markings should I look for verify if they're on the correct sides? Any ideas on anything I may have missed?
 
My torsion bar adjustment is the same as you mention(more on 1 side).Why?I don,t know either.I think you should take it for alignment,espeacially after doing UCA bushings and the LCA bushings and adjusting your ride height.This will throw off your alignment for sure.Take it in while everything is fresh and new,it will give you piece of mind in the long run.Good luck.
 
I plan on getting it aligned as soon as I get all this sorted out. Before I changed the bushings, I was at least able to get it to the specified ride height (1 7/8") which is a measurement of the lowest part of the adjusting blade to the ground minus the distance of the lower ball joint to the ground. Closest I can get is 1 3/4". When I popped out the left torsion bar, I noticed some numbers and a letter "R". I forget what the numbers were, but does the "R" mean it's supposed to be the right torsion bar? If so, I either have 2 rights, or they are reversed. I'm going right now to take the right one out and see if it's marked with an "L".
 
From what I've heard once they are installed on a side it's better to leave them that way than to change them, but some of that might depend on how old you think they are. I think once they get used to twisting one way you wouldn't want to try to twist them back the other or they might fatigue worse.
 
I saw somewhere that drag torsion bars have 90 lb/ft, and /6 bars have either 100 or 110 lb/ft, and I think the 110 rated ones were also in 318 cars (so probably what I have). Would a set of the /6 bars be good for drag racing? Engine is a small block, battery is in trunk.
 
there are many of reasons that it could do that. 1 check your strut bushings, if they are worn that will make the entire frame shake. Also check to see if your driveshaft is out if balance, that will also shake your car like mad. you might also have to check your tires, they may have a flat spot OR the belt moved inside the rubber of the tire. best way to check that is to rotate the tires, or check for lateral runout of the tire. most likly it's your driveshaft. Mine does that around 75mph, and it's on my list of things to do. a place around here does it for $60
 
I've since replaced the strut rod bushings and LCA bushings. Gave the gas a little blast the other day, and there's still vibrations, but not as bad. I'm waiting on a reply from another forum member on a set of /6 torsion bars, and once I get them, I'll get it aligned. If it's still doing it, then I guess I'll get the driveshaft checked, but it's a new driveshaft, and was supposedly balanced. As for the tires, I have 165's in front and 265's in the back, so I can't rotate them, but they are all new tires and it doesn't feel like a tire out of balance.
 
My Cuda has the left torsion bar cranked in a lot farther than the right. I thought it might be a weak bar and replaced them but it's still the same. It doesn't make sense either cause the engines on A-bodies are offset 1-3/4" to the pass side so you'd think you would have to crank the pass side bar more cause the weight is shifted that way. Go figure!!

/6 torsion bars are good drag bars because they react quicker to transfer weight. Only problem with them on the street is their so light it won't handle as well.

If yours were installed wrong I wouldn't swap them around. I'd replace them.
 
fishy68 said:
My Cuda has the left torsion bar cranked in a lot farther than the right. I thought it might be a weak bar and replaced them but it's still the same. It doesn't make sense either cause the engines on A-bodies are offset 1-3/4" to the pass side so you'd think you would have to crank the pass side bar more cause the weight is shifted that way. Go figure!!

/6 torsion bars are good drag bars because they react quicker to transfer weight. Only problem with them on the street is their so light it won't handle as well.

If yours were installed wrong I wouldn't swap them around. I'd replace them.
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I figured the passenger side would need cranked up more, too. My driver side is cranked about 3 threads from being tightened completely, but the passenger side is less than halfway in. Weird how that works, but pettyblue said his are the same way. I'm sure there's someone around who knows why. Maybe to have the right one stiffer for circle track?
 
Very rarely are the torsion bars cranked equally.
 
well hopfully it's not your tires, even new ones can wobble. sometimes the belt inside the tire is put in correctly from the factory so it makes the car rumble up and down, called tramp. I'de bet it's the driveshaft though
 
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