I am hearing a grinding or rubbing sound in the rear end when I am driving. Its hard to describe it but I am going to say its like a hollow sound, like its echoing somewhere. It sounds like it may be in the wheelwell or the axle. I put it on a lift and rotated the tires and didnt hear anything. I also turned both rear rotors, didnt fix the problem. I fear its inside the axle. It is not constant. sounds like something is hitting one certain spot during each revolution. Sound speeds up (a little) at higher speeds. Has anyone had this problem or know what it may be.