Need some help here!!! I have a grinding noise that just started yesterday coming back from a trip to Galveston. Had no problems on the trip down. On the trip back we got about 20 miles from home when it started. Did it twice on the interstate for a short time then stopped. Got off on our exit and it did it continuously until we parked at the house. Kind of sounds like when you driving over a bridge that has the metal grates. Any ideas on what it might be??