How to replace Axle bearing ?
How to replace Axle bearing ? 
If the sound reminds you of a 4 wheel drive coming down the road, then its probably your rotor warped that caused piting on your axle where it has the warp puttin undue pressure on the axle everytime it pushes on the wheel bearing when the warp passes by. I've had it happen twice...replaced the AXLE both times ( very obvious on the axle). First time I replaced rear end and all but used the same rotor. The second time, I tried to turn the rotors but were to warped ( had to buy nre ones). To answer your initial question, you have to drain the rear end, pull the axle, pull the seals, rent or buy a bearing puller to pop out the bearing because they are pressed in. Pulling th bearing is easy, getting to it is time consuming.
