Chrysler Repair: 2008 Sebring vibration issues, chrysler sebring, brake calipers

Question
My car is a 2008 Chrysler Sebring Hardtop convertible Limited 3.5L
Here is a little bit of history, I bought the car with 4k miles on it and had to have the rotors replaced, and a few other things since but the real issues started,

In Feb  2010 I took my car into the dealership for a whining noise upon startup, at the same time they rotated my tires. Ever since then I have had a vibration in the car felt in the seat and the steering wheel, the dealership replaced all of my tires, did not fix the issue. I then took the car to discount tire to have the tires balanced still did not fix the issue. Not being satisfied I then took the car to another dealership they said they could not duplicate the issue, told me it was the rim they did an alignment and road forced balanced the tires, still a vibration, took the car to discount tire again they said the rims were fine. Brought the car back to the dealership again, had them take the tires off a new line car and go a test drive with me and the service manager,Still no change. Dealership had a tech specialist come in said he could not see or feel an issue, one more thing they said they would do would have the service rep with a special machine come test the car. To get him there will take 3-4 weeks, in the mean time I'm driving a car that feels like a truck.

Question what should I have them look for? Since it seems they can't find the problem and they are not willing to spend the time to find the problem.

Answer
Hi Michaela,
About the only question the history of this problem suggests to me is why did the rotors have to be replaced at such low mileage? Is it possible that the brake calipers are not sliding freely on their guide pins which then causes them to drag, overheat, and vibrate?  To test this possibility: When you have been driving for a while and have been feeling the vibration I would slow gradually to a stop (without using the brakes) and then get out of the car and touch each of the four rims to see if any one of them is hot to the touch. If not, then the brakes are not the cause of your vibration. If so, that is a distinct possibility.
Roland
PS Sorry for the delay but I recently noticed your question in the 'pool' to which the other expert had referred it. Please 'rate' my answer, and where you see the question about 'volunteer of the month' please consider giving me a 'yes' answer. Thanks