I have a 2003 for explorer Eddie bBaue with 200,000k. Today when I pulled out of my driveway I heard a grinding sound coming from under my SUV. I no it wasn’t coming from the bearings. I could feel the grinding. When I put it in drive and I stepped on the gas it got louder as I got down the street. I can tell it’s in the middle of my SUV but in the back. Any clue as to what it could be?