This evening I was in the garage and heard a humming sound somewhere between the back wheels of my 2010 4R Limited. Seemed to be somewhat louder on the driver side. The 4R was locked and had not been driven for at least 4 hours. The temperature in the garage is about 40 F. Never heard this before. The only thing that I have done recently is change my summer wheels and tires to my winter wheels and tires and drive in about 3" of snow across town and back today. Seems strange, but maybe someone knows what is going on. Thanks for any help you can give me!