Thread: Highway vibrations... (checked the usual)

Hi! New to the forums... I just bought a 2005 Grand Prix GT... but I am having some issues, and I can't resolve them... (mind you I am a mechanic... so this is getting frustrating...) I havea vibration, which can show up any time between 45 and 75... it is there more harshly upon acceleration, and eases up some when I let of the gas. (all these repairs within the last week)... I replaced all four tires. Replaced the rear brakes and wheel bearing... (had some runout in the hub surface)... replace the front brakes, replaced both front cv axles with new ones (not remanufactured)... replace the main engine mount on the passenger side by the balancer. I can take the wheels off the car, take the front brakes completely down to the hubs.... The vehicle will shake the entire two post rack, you can see the engine bobbing up and down a little... so I have completely illiminated the brakes and tires as a problem. And with axles replaced... I am at a loss here... is there a trans issue which could be causing a vibration...? The CV shafts seem kind of loose to me where they go into the transmission... I'm sure there should be a little bit of play... but I think it might be a little much. The engine runs great, and the trans shifts smoothly. I have good plans for this car, but I'm not gonna do anything til I can get this resolved... any help would be REALLY appreciated...

I didn't notice any defects really in the trans mount, but I may try replaceing that anyhow. The dogbone mounts seemed a little squishy, but not any more really then other cars I see come into the shop regularly. I did take my Matco Determinator home with me tonight and watched the misfire datastream all the way home for 30 minutes, along with some trans data, and I didn't notice any misfires at all, or any trans data that seemed out of the normal... I am worried about the amount of play that was present in the output shaft. I could just grab it with my fingers and move it all around freely. I am wondering can a output shaft seal warp... cv shaft bearing be worn badly...? I looked at the needle bearings and didn't notice any signs of wear on them... I am over all happy with everything else about the car. I am just getting really frustrated with the vibration issue at this point.

Although putting in the engine mount seemed overly hard compared to others I have replaced now that I think about it, I just couldn't get it to line up for the life of me :P no matter how big the prybar... seemed like the engine wanted to be forward in the lower right corner. Never really noticed that much trouble before, and I have done quite a few of these to do oil pan gaskets.

Flip them? Just unbolt them, turn them over, and rebolt....?

and I meant to say can an output shaft warp? (not output shaft seal)

Anyone ever got a bent NEW axle. (Not reman....)

New engine mount.... new tranny mount. Flipped the torque arm bushings. 2 new rear bearings. 4 new rotors and all pads. 4 new tires. Ten times balancing. Rotated. NEW axles. New intermediate shaft. Vehicle vibrates on a two post lift... with tires and brakes removed. And i did have stands under the control arms so they werent hanging freely. Harshest at 65-68. And it isn't a slight vibration. Worse on acceleration. Vehicle runs great. No codes. No pending codes. No misfire counts. All of this in the last week. Ive only owned it a week. I am so beyond frustrated... :-(

Lol... not a great answer. Drive straight... wheels straight. Lol... I've never seen an alignment cause a vibration... but I haven't checked. Im just starting ti think the problem is unsolvable.

No... subframe is real nice and clean... who car is amazing except for this issue. I am thinking maybe I got a bad cv axle. Ill check runout on the center of the shaft tomorrow if I have time... Idk what else... I would do an alignment... im just afraid im gonna have to keep redoing everything.

Mounting run-out guage to a solid non moving surface around the shaft. Setting the pintle of the guage on the center of the axle shaft. And spinning the shaft by hand.