I have a 1998 lesabre with 135000 miles. It begins to vibrate at about 45mph and continues gradually getting worse the faster I go. At 60 or 65 it's agravating and uncomfortable. I've changed tires and rims. Where do I look next to diagnose the problem? The car was like this when I bought it but I just figured it needed tire balancing. Thats about what it feels like, a real low tire or a tire way outta balance. Prior to this buick I had a 93 and a 96 lesabre and they both floated down the road like a dream so I know this isn't a normal ride for a lesabre. I appreciate any advise or suggestions I can get.
Thanks