general problems of the 2004 Buick Lesabre

Several attempts were made to correct a problem with my 2004 Buick Lesabre. I have been dealing with a rep from gm motors without success. He just kept stringing me along saying he would call, at first it was every week then every three days - each time saying he was conducting an ivestigation into the problem. The car was purchased Aug 17, 2004 and the problem has existed since "day one"! I do not feel the car is safe! it has been back to the dealer several times. A re-purchase was supposed to be in the works but I guess they don't want the car either! not only are the seat covers bad but the vehicle keeps vibrating/wobbling! I have all the work orders (except for some verble comments) to support my complaint. I bought a new car I believe I should own a new car! please help me get this situation cleared up and me on the road with a new car(safe) like was purchased in the first place! I was going to resort to reporting to the attorney general but I'm hoping this form will help me out.

I purchased a used 2004 Buick Lesabre with 18000 miles. I can feel a vibration in my feet, seat, and the steering wheel at speeds above 60mph. The dealer checked the tires and replaced the right front tire saying it was out of round and that all the other tires were in balance and within spec. S. I have driven it for severals day now and I can't discern any improvement. I called the service dept. Back this morning and they recommended I purchase a $566 set of new tires! I think the problem is in the drivetrain but they won't even discuss that possibility.