i have a 2003 galant. i bought it used. there is a problem that i dont know what it is! when i go through a small pot hole or a minor bump the rear end of the car shakes left to right like as if it is sitting on an untightened bar that the body shakes left to right (almost a jerky slap of the fishtail) Does anyone know what that is?! PLease help! also the car when driving to work this morning it was a little wet and rainy the rear end was swaying left to right lilke a fish tail slowly but steadily. freaked me out! please help!