2002 Chevrolet Avalanche 30,000 miles. I just recently went on a long road trip. On the way back I noticed a road noise that sounded like a humming/whining noise something like extra large tires make on a vehicle. When I speed up it gets louder and when I slow down it gets softer. It even makes it while just coasting. The tire tread is good and I tried rotating them to see if it would fix it but it did no good what so ever. Do you know what this could be?