Let me tell you, 4.77's make some noise! I figure my new mud tires will help mask that humming! And just the opposite of the first post... if you start to hear a racket when you take your foot off the gas when going down the highway, it could be the preload on your pinion is too tight or too loose. Either way, the pinion bearings create a lot of noise and a lot of heat when they are out of spec.