Does anybody else hear a clunking noise when you put your truck into reverse? It sounds like metal-to-metal. My dad's 2000 F-150 supercrew did this, and Ford had to replace the seal on the differential three time over 3 years. It seems to do it after the truck has been driven a while. I always notice it when I back my truck into the driveway. She will be going in for her first oil change (1000 miles) nest week and I am going to have them check it out, just wondered if anybody else has heard this?