I found out about the humming. It is a rear differential. I bit my bullet and took it to the Toy Stealer. Checked out that rear differential is bad but not severe enough to replace it. What the heck is that mean? To recap what is going on, I heard a humming sound over 65mph driving hwy. So, what to do what to do...... Stealer said it would be close to $2500 to replace. I am going to drive it since it is not severe to NOT drive according to them. What do you guys think? Am I SOL?