Intermittent Front End Noise/Vibration in a 2006 Malibu Maxx

I bought a used Malibu Maxx,with only 29,000 miles on it from a local GM dealer a little over a year ago. The vehicle now has approximately 58,000 miles on. My wife uses the car to go to and from work approximately 500 miles per week. We have the 100,000 mile extended warranty on the car, but have recently been having intermittent problems which our local GM dealer is unable to duplicate in order to rectify them. At around 70 mph while driving on the interstate, a vibration will start from the passenger?s side and progress over to the driver?s side. It starts out softly and by the time it reaches the driver?s side it is extremely loud and can be felt thru the steering wheel. It almost sounds like you have a flat tire or that you are driving on the ?rumble? strips that they have along the edges of the highway. If the brakes are applied in order to slow down while this is happening, it gets even worse and feels like the whole front end of the car is going to fall off. This problem does not happen every time the car is driven, however. When it does occur, it will last for a distance of 2 or 3 miles, which seems like an eternity while this is going on at 70 mph. I have had my driver?s license for over 40 years, and I can tell you that this honestly scares the hell out of me.

After 2 or 3 miles, this vibration will gradually fade away as if it never happened in the first place. Our local GM dealer checked the car out after I had given them as much detail as I could in order to help them find and correct the problem. The only thing that they could find wrong with the front end was a bad outer tie rod end, which was replaced under warranty, and the front end was re-aligned. I have also had the brake pads replaced all the way around on this vehicle. The vehicle has apparently thrown no fault codes that the dealership?s diagnostic equipment can find. I have had the tire balance rechecked, and it is fine. My extended warranty is only good for 100,000 miles or Jan. 2012, whichever comes first. I got laid off from my job 6 weeks ago, and money is kind of tight until I find new employment. I can’t afford the “shotgun” approach to fixing this, and I am afraid that I will not be able to get this problem corrected at this rate. I am at my wits end, and don?t know what to do here.Can anyone suggest what else I should be looking at to fix this? One thing I did notice when this happened to me while driving the car is that the accelerator pedal got kind of stiff and took more effort than normal to depress.

I feel that this is a dangerous safety issue when this problem is occurring. Should I try another Chevrolet dealer?