VIBRATION WHILE ACCELERATING

  • Tiny
  • Smurfman
  • PONTIAC GRAND PRIX

2000 Pon Grand Prix GTP, 113,000 Miles, v6 3.8 SuperCharged
At about 45-60 MPH only while accelerating - or holding the speed at say 55. I have a vibration, that acts like a tire out of balance, either that or the wheel is going to fall off.

The vibration is almost invisable at 65-70 MPH

The worst vibration comes while accelerating from 40-45 MPH while corning to the right only, that is where the wheel feels like it is going to fall off. To the left, it is not really apparent.

At higher speeds 60-70 and hitting a corner, the vibration becomes more of pulsating that can be felt.

Most of the vibration is not felt in the steering wheel, but rather my legs, not so much my "backside", as I have heard that with some vibrations - steering wheel is the front end, seat is rear end.

I was reading some posts about CV joints, could this be what I am looking at?

I was starting think transmission, but it really runs well and responsive all other times.

I thought spark or timing, my plugs and wires were replaced last summer (12-13K ago), timing, I was not sure (there is a muffler noise, towards the front, I have not looked into, perhaps a hole in a pipe, but it is not overly loud) as for timing, it really idles well, runs with good speed and the Super Charger kicks in as expected.

Any idaes, or troubleshooting - much appreciated.
J

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Friday, April 20th, 2007 AT 10:56 AM

7 Replies

  • Tiny
  • NickyD01
  • MEMBER

Your first thought is most likely the problem. You say the vibration changes with speed. That tells me that it is not an engine or transmission problem at all. If you had warped rotors it would vibrate upon braking. The other possible problem could be tie rod ends but the tie rod ends will occur most likely more steady and on braking. It would be a good idea to have your tires balanced at a cheap price to find out if that is the problem or not.

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Friday, April 20th, 2007 AT 10:47 PM
  • Tiny
  • DataPAcks
  • MEMBER

Hi Smurfman

Did you ever figure out what this vibration problem was?

I'm having the same problem exactly. So far the GM dealer diagnosed it as a front bearing. That cost $500 and was wrong. The Goodyear dealer diagnosed it as a bad tire. That cost $500 and was wrong. Mr. Transmission thought it had to do with the engine and suggested I change the Mass Airflow Sensor as the check engine light was on and that was the reason it was on. That cost $550 and was wrong but was needed anyway. It started leaking a little antifreeze at the center head and cylinder head at the back bank so a friend recommended his mechanic. He did turn out pretty good and he changed the intake manifold, supercharger and valve cover gaskets. That cost $700 and did not do anything for the vibration. This mechanic thought the engine was sucking air threw the bad gaskets and figured the vibration would be corrected with this repair as well. It didn't, Although I have full supercharger boost back that I didn't even realize that I had been loosing. I've also had the front control arm bushings changed and the front end all checked out. Apparently it's OK. The brakes pads, rotor, calipers and flex lines were all changed within the year and have less then 20 k on them.

As you can tell, I have $2200 invested in trying to solve this vibration and all I've managed to fix are a few others things. It actually puts me in a bad mood just driving it. I would really like to destroy it and collect the insurance but I don't have the demeanor for that.

Please share you experience with me!

Bill

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Tuesday, February 5th, 2008 AT 7:00 PM
  • Tiny
  • Nobodyhome923
  • MEMBER

Your axles could be the source of your problem.

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Wednesday, March 11th, 2009 AT 2:19 PM
  • Tiny
  • Rockerpaluza
  • MEMBER

Do you found the actual cause of this problem?
I have the same prob here.

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Monday, March 29th, 2010 AT 2:07 AM
  • Tiny
  • Mschillingii
  • MEMBER

Most likely cv axles i'm having the same problem thats what it is. It will keep getting worse and worse till they are replaced. I did both front bearing and mine still does it.

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Monday, July 5th, 2010 AT 2:21 PM
  • Tiny
  • Dave's Big Backyard!
  • EXPERT
  • 264 POSTS

A bad cv joint will make the whole car shake under tork this is one of the inbord joint on the c.V axl, sometimes it wont do it till its been driven for a while.

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Tuesday, April 5th, 2011 AT 11:22 PM
  • Tiny
  • Rick57
  • MEMBER

2000 GTP. Having the same problem. Wicked shimmy making it un drivable and unsafe at freeway speeds. Its not side to side more like a bounce up and down on freeway speeds over 50 under load on acceleration. Smooth as silk when it not under load or in town. Broken motor mounts will cause this problem as well. Midus in Redding California worked on my problem but still it is unresolved. Changed motor mounts, tie rods and all 4 struts plus a fluid change in brake system costing me. $2,375.00. I brought it in for this problem and they fixed everything else but what I brought it in for. Midus said it was a list of possible things. Torque converter sticking, Supercharger belt system vibrating and some reasons even an idiot would know better. But the bottom line is they just wanted to take more of my money. Hell of a way to get return business I would say. Part changers. Not real mechanics that work the problem those days are gone.

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Thursday, September 22nd, 2016 AT 12:20 PM

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