Mileage is 56,000 and this engine rattling seems to be getting worse. Ford says it is normal ???????????. Passengers say "Is this a diesel?". Seems to go away when torque converter lock-up occurs. Not heat shields or anything under the truck. My extended warranty goes out at 60K and I don't want to be left holding the bag. I see a lot of posts about the 4.0 v6 having tensioner problems but haven't found one regarding the V8. Otherwise engine runs good, gets good gas mileage and uses no oil. I have always used Mobil 1 and changed it each 5,000 miles or less. Any suggestions??? Thanks