While driving my '06 G6 GT , I've noticed there to be a thumping sound that gets louder and faster as speed increases. Also, theres is a very faint squeeking sound that I can hear if it's very quiet (no radio, etc). I think it is coming from the rear left side. I've taken both the front and rear left side tires off and everything seems to look good. Any idea on what it might be? I haven't found anything online that matches BOTH these symptoms, but two ideas I've seen were possibly unevenly worn tires or shot wheel bearings. Please help guys!! Thanks!