I have an 09 mustang GT that I bought a year ago and my rear end just starting making a funny noise. I only hear it when I turn either way and it gets louder the longer i drive it. It kind of sounds like I rubbing noise. The mechanic I brought it to said he was sure that it was the rear differential that needed to be serviced. He did the work I drove it home and the noise is still there. Any ideas would help.