I have 2WD with 6,000 miles. Recently when braking over a road that isn't smooth there is a squeaking & sometimes creaking noise. If I am not braking over a bumpy road there is no noise, if I brake on a smooth surface there is no noise. Just over cracks, bumps, with medium to hard pressure... It tends to get less after 30 minutes of driving. The service dept worked on the rotors, but that hasn't helped. Any thoughts what it might be. I will be going back in again soon to have them figure this out.