I have a 2007 G6 4cyl 4 door automatic bought new and now has 108,000 miles. Last week I was out of town and it developed a humming in the front end above 25 mph. My wife had the left wheel bearing replaced and it got slightly better she says, but not cured. When I got home I swapped tires front to rear and the sound is still in the front. The sound is definitely rotational-drive or neutral, on the gas or off, uphill or coasting, braking or driving-nothing matters it is a constant speed related humming. You can really hear it inside with windows up and a/c off. With windows down there is too much wind noise. It sounds like quiet mudgrips almost. Any suggestions? I can throw another wheelbearing at it, but I really don't think that is it. I am very mechanical, and my gut says this is not a wheelbearing. Is there any issues with differential carrier bearings in the transaxles on these? It has really been a good little car with no issues until now. Changed the trans fluid with Valvoline synthetic just before 100K. Tires are Michelin X-Energy with about 25K. Brake pads are at least 1/2 left. Half shalves look good-not loose, no clicking, boots are good. Thank you for any advice.