I am new here and have been lurking for a while. We just recently started seeing sub zero temperatures here in Ontario and I have just noticed a knock in my 07 Denali XL when I first start on my way when the engine is cold. Reading the forums I see some members have had problems with the 06 and older models but I have not seen anyone with 07's and newer. Has anyone else had the same problems? Sugestions on whether or not GM will do anything about it?