My Explorer is making a shifting noise in the rear end when I brake or turn suddenly. It's almost like something is moving around though it is clearly coming from the exterior of the vehicle and not the cargo area. I was told that this could be my shocks, but I haven't had them checked yet as the ride of the vehicle has not changed. The brakes are still working properly. Other than the noise itself, nothing has changed in the way the vehicle handles. Any ideas? Thank you.