I have a 2000 silverado 4wd. I was getting a humming noise from what sounds like the front end (hard to tell). I can hear it best when on the highway at about 65mph. I notice it more when i let off the gas, although I think it still remains while giving it gas. The noise does not go away when I swerve from side to side. I thought it might be wheel bearing but I wasnt sure what side. I bought a new one and put it on the drivers side. The noise remained so I put it on passenger side and that didnt help either. If it is not wheel bearing, what else could it be? The sound it makes is like driving down the highway with huge tires on.