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Vibration at 45 mph after replacing torsion bars

Posted By: taboo

Vibration at 45 mph after replacing torsion bars - 01/30/15 04:41 AM

My wife and I purchased a 71 challenger 440 six pack 4 speed car, that was originally a 318 automatic car. We both enjoy working on the car but we are stumped on this one.

The car drove well when we originally purchased it but had a noticeable vibration at 75mph for the first year. We later noticed the car was bottomed out on the lower control arm bumpers. We ended up replacing the torsion bars with 0.96" bars and we were able to get the car ride height corrected (the old torsion bars were actually swapped right and left and were clearly worn out). We took the car to a chain store to get the alignment done afterwards and ever since then we have had a violent vibration that starts at 45mph that seems to settle out at 55 mph and have nearly no vibration at 60+. The vibration occurs at these speeds even if I take it out of gear. Also, I believe it is in the rear as I do not feel it in the steering wheel.

I thought the problem was the tires as they were 10+ years old, so we ended up changing both the wheels and tires, but still have the same issue. I was wondering what the next troubleshooting step would be. Any help would be greatly appreciated!
Posted By: ahy

Re: Vibration at 45 mph after replacing torsion bars - 01/30/15 05:12 AM

As a start in troubleshooting, changing the T bars should not affect the rear. Sounds like the shakes came before wheel/tire replacement. For trouble shooting, as it may be in the rear suggest 1) check rear U joints for slop 2) put the front on ramps and with a helper to turn the wheel, check for slop in front end joints 3) Get it aligned and re-balanced at a good shop. There are not a lot of shops that are good with T bar suspension. A good tech will check tires for out of round at least visually while balancing. 4) Report back.
Posted By: mopar_man

Re: Vibration at 45 mph after replacing torsion bars - 01/30/15 05:23 AM

Quote:

As a start in troubleshooting, changing the T bars should not affect the rear. Sounds like the shakes came before wheel/tire replacement. For trouble shooting, as it may be in the rear suggest 1) check rear U joints for slop 2) put the front on ramps and with a helper to turn the wheel, check for slop in front end joints 3) Get it aligned and re-balanced at a good shop. There are not a lot of shops that are good with T bar suspension. A good tech will check tires for out of round at least visually while balancing. 4) Report back.



And there lies the problem . A tire can be perfectly balanced but still be out of round. have tires checked for out of roundness and balance again . check drive shaft and u joints , sometime a bad shock with a little out of balance can seem like a real bad balance issue .
Posted By: RobG

Re: Vibration at 45 mph after replacing torsion bars - 01/30/15 05:30 AM

I had a similar issues at around 60MPH. The rear tire tread on my BFGs was separating.

2 new tires in the back and it all went away.
Posted By: skicker

Re: Vibration at 45 mph after replacing torsion bars - 01/30/15 05:46 AM

I had a vibration in a Dart years ago. A buddy of mine had me unhook the drive shaft and rotate it 180* and hook it back up. It didn't fix it but it reduced it.
Posted By: taboo

Re: Vibration at 45 mph after replacing torsion bars - 01/30/15 05:46 AM

Thank you for the quick replies. I should mention that I actually replaced (not changed) all 4 wheels and tires with new and had them balanced. There was no change in the vibration after doing this. I will look in to the other suggestions. Thank you!
Posted By: Kern Dog

Re: Vibration at 45 mph after replacing torsion bars - 01/30/15 05:53 AM

Quote:

I had a vibration in a Dart years ago. A buddy of mine had me unhook the drive shaft and rotate it 180* and hook it back up. It didn't fix it but it reduced it.



?????
This is interesting!
Posted By: rowin4

Re: Vibration at 45 mph after replacing torsion bars - 01/30/15 06:08 AM

Jack the car up, put jack stands under the rear end. Start the car, put it in gear and give it some gas. You should be able to see if it is a bent rim, bad tire, or drive shaft problem.
Posted By: RapidRobert

Re: Vibration at 45 mph after replacing torsion bars - 01/30/15 06:52 AM

shaft/ujoints/extension housing bushing
Posted By: moparpoolman

Re: Vibration at 45 mph after replacing torsion bars - 01/30/15 12:27 PM

Quote:

Thank you for the quick replies. I should mention that I actually replaced (not changed) all 4 wheels and tires with new and had them balanced. There was no change in the vibration after doing this. I will look in to the other suggestions. Thank you!



You're probably noticing the vibration more after torsion bars installed because the car is stiffer/more rigid. What kind of tires did you put on the car? I've seen many of the repro tires "out of round" and balancing can not fix that. I'd also check the transmission mount.
Posted By: Paul_Fancsali

Re: Vibration at 45 mph after replacing torsion bars - 01/30/15 10:03 PM

Did anyone dent the driveshaft ?They did that at the one shop I had my car I had to replace the shaft
Posted By: azmopar

Re: Vibration at 45 mph after replacing torsion bars - 01/30/15 10:06 PM

Quote:

Quote:

I had a vibration in a Dart years ago. A buddy of mine had me unhook the drive shaft and rotate it 180* and hook it back up. It didn't fix it but it reduced it.



?????
This is interesting!



I did the same thing on my challenger it reduced it to almost nothing
Posted By: GeorgeH

Re: Vibration at 45 mph after replacing torsion bars - 01/30/15 10:24 PM

a little too much axle runout can cause a vibration that comes and goes.
Posted By: feets

Re: Vibration at 45 mph after replacing torsion bars - 01/31/15 01:11 AM

Quote:

shaft/ujoints/extension housing bushing



Transmission mount can do this too.
Posted By: TC@HP2

Re: Vibration at 45 mph after replacing torsion bars - 01/31/15 05:51 AM

Quote:

Did anyone dent the driveshaft ?They did that at the one shop I had my car I had to replace the shaft



As can a driveshaft that is too short.
Posted By: Kern Dog

Re: Vibration at 45 mph after replacing torsion bars - 01/31/15 09:26 AM

Quote:

Jack the car up, put jack stands under the rear end. Start the car, put it in gear and give it some gas. You should be able to see if it is a bent rim, bad tire, or drive shaft problem.




I did this once when I had a bad vibration in a ONE ton Dodge truck. You'd think the mass of a truck that heavy wouldn't vibrate much. It turns out that one of the FREE tires a buddy gave me was on a seriously bent wheel. I'm talking a wheel that was bent at least 1 1/2 inches! After pulling the wheel, I could clearly see the bend in the center section. I looked at the other three wheels and two others were AFU as well.
SOME buddy, huh???
Posted By: 71GTX471

Re: Vibration at 45 mph after replacing torsion bars - 01/31/15 03:38 PM

What condition are the lower control arm bushings in.
Posted By: RapidRobert

Re: Vibration at 45 mph after replacing torsion bars - 01/31/15 06:07 PM

Quote:

As can a driveshaft that is too short.

that was the prob with my 65 dart 318/904/7&1/4, not enough front yoke engagement into the trans. It would vibrate part time. rounded up a slightly longer shaft/swapped the front yoke/ujoints & all good. The tip off was that I could see on the front yoke where it was worn smooth on a prior vehicle but now alot of that length was surface rusted as it was not engaging into the trans (wrong shaft or wrong yoke)
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