I purchased a 2007R/T in Feb. A manager was driving it. It has 6700 on it now. It. Making a chattering noise from the front end. At times it seems to get louder. Two dealerships called Chrysler and they know about the problem? But they don't what it is and they don't know how to fix it? They say it is safe to drive? How do they know if they don't know what's wrong, or fixing it?