I have a 2003 Cadillac Escalade. On the way to taking my vehicle to be serviced, I began to hear a low humming noise in the center rear of the car.I had the oil changed and was told that I needed rear shocks. Considering that I was not convienced that the shocks where bad. I went and had a second opinion and was told that the shock wear ok and the vibration was due to the rear differitial and that possibly some bearings had gone bad. Needless to say I am exspecting a nice price for repairs, but I wanted a ball park figure to work with. So at least I will know if I am being ripped off. Thank you.