Rusty

So I have this random weird vibration/shaking/jerking issue with the cobalt. It’s hard to explain exactly what it is or when exactly it happens, but I’ll certainly try. I’m going to bring it in to the dealer when I get a chance, but in the meantime I wanted to get some ideas of what it could be…

This basically seems to happen at low speeds and low RPM. Typically 2nd gear under 2k RPM and 3rd gear under 2k RPM going under 40mph is when it is most prominent. It seems more pronounced under very light acceleration, but can also be felt on decel and braking. The best way for me to describe it would be if you imagine some rotating component (rotor/hub, driveshaft, axle) and stick a weight on it. Think about how it would vibrate or feel jerky because of the lack of balance. It feels kind of jerky as if the motor was hesitating when you try to accelerate, but it is not matched to the engine RPM, rather it seems to be matched to the speed of the car (rotation of the wheels).

I thought maybe it was that my wheels need to be re-balanced as I got new all-season tires a few months ago and may not have been balanced properly. However, I do not get ANY vibration at highway speeds as I’ve felt before with unbalanced wheels.

Other than that I have no clude. It’s an 08 cobalt turbocharged who’s only mods are short shifter, HID lights, and these new all-season (Dunlop) tires. I just wanted to put this up to get some ideas for my own piece of mind. I know many parts manufacturors for GM have gone under and I heard horror stories of people waiting months for parts. Thanks.

Permafried-

Hmm...I know my dealership had issues balancing the wheels/tires when I purchased my winters, they couldn't use the typical machine they had to do something called a "forced balance" but my severe vibration was around the 50 - 60 mph range. There was a TSB related to a certain range of rotors (mine falls into it but no issues yet so I'm not touching it) causing a vibration at lower speeds, I'll have to try find it back.

Does the vibration feel like it's jerking left/righ or back/forth? I'm wondering if you're feeling the crank since I know in my 2.2 at lower RPM if I got on it I could feel the torque from the crank picking up, but these are just some random ideas.

Permafried-

Rusty

Yea, well I had my old high school shop teacher do mount and balance the tires because he said he can do it for free at the school's shop. He messed up a valve stem and didn't tighten it down all the way. The next morning after I picked it up it was almost completely flat. I'm guessing he didn't balance them right either. But what gets me is that this was done in like October or EARLY November. I don't know why it would be fine now and then all of a sudden be a problem months later.

In any case, it got really bad today as the car started vibrating wildly on the highway at about 60mph. So instead of risking any further damage, I just dropped it off at the dealer. I know I will get raped to get it fixed, but I had no other choice as I didn't feel safe driving it any longer. Just too bad I'm right in the middle of building a new motor for my other car. Now I have no cars to drive!

krispy

When vibration gets progressively worse in a quick amount of time its always a good idea to check the lug nuts.

Rusty

Well turns out I apparently hit some major pothole or something. They said I royally messed up the belts inside the tire and the tire was trashed. There was several bubbles in the sidewall. They replaced the tire, mounted and balanced it and I took it home today. $230 later, but it was fixed in a day.

Rusty

This morning I wake up to a tire with 8psi in it. The sidewall was collapsed under the rim. I drove down the road and filled it with air. The sidewall looks damaged (cut). It held air ok on my way to work, but I didn't feel good about it. I bet it will loose at least 10psi by the time I leave work too.

I called the dealership and told them. The guys exact words were "oh ****." So I'm taking it back tomorrow so they can give me a loaner car and I can feel awesome driving home an aveo.

At least this is more motivation to get my other car (Talon) running.

Permafried-

I'd be willing to bet the rim is somewhat out of shape from cranking a pothole or the dummies didn't mount it 100% correctly and there's a small leak (though dropping to 8psi it may be substantial). Into the leak tank the wheel goes...hope they get it right this time .

Rusty

They said the balanced the rim and it looked ok. My visual inspection didn't reveal anything wrong either (THANK GOD!). And yea, I hope they get it right this time too!!!