I recently picked up my 04 CC 4x4 and it now has about 300 miles on it. When traveling down the highway at about 56-58 mph, a resonance can be heard in the driveline. I'm not sure whether this comes from an unbalanced driveshaft, rear differential, or possibly just wind howl. However, the sound/vibration always reappears at the same speed. If anyone can help me determine if my truck is the only one doing this, I would appreciate it. Also, when the engine is running and I stand near the front of the truck, I hear a clicking sound that seems to come from the belt. It can be heard on one side, then the other side, seeming to travel with the belt. If anyone could give me a hand/clue as to what these issues are, or if they are in fact issues, I will greatly appreciate it. ....thanks in advance.