About a month ago my cobalt started this weird vibration on the highway. It only happens after I have been going 70-80 for 5-20 minutes on the highway. The vibration will start very mild and slowly get worse and worse. Within 30 seconds the whole car is shaking. I'll put my flashers on and begin to slow down. The vibration occurs until I come to a complete stop. When I apply the breaks, the steering wheel shakes. As soon as I come to a complete stop I can get back on the highway and drive with no problems for the rest of the trip. I have already replaced front wheel bearings, tires balanced and rotated, engine mount, transmission mount, sway bar end links, new brake rotors and pads all the way around and rear shocks. The shop I have taken it to has no clue. I'm tired of throwing parts on it and the problem not being fixed. Any ideas or suggestions.

 

Any popping noises or anything when turning? Looks like you replaced everything but your axles

 

Nope. Both shafts look good and the boots aren't torn.

 

Have you checked the Control arm bushings?

 

Clean your wheels.

Dirt/brake dust can accumulate in the ridges and contours of the wheels thus throwing the wheel/tire off balance, and creating the vibration.

I never noticed this until I got Enkei M52s. They hold brake dust and dirt like no other. After a good cleaning the vibration always goes away.

 

I had a similar problem on a Jeep that had bad tires with flat spots. The problem wouldn't go away after stopping, it would just be less noticeable at lower speed. Have you ever locked up the tires, had a bad skid, or let the car sit for a very long time?

 

I had a similar problem, and it was the control arm bushings. Braking would cause the wheels & control arms to shake back and forth, which would shake the steering wheel. They didn't look bad upon inspection, but the steel sleeve in the bushing completely fell out when I removed them.