2002 F-350 -Metalic tapping sound when pulling uphill
I have a 2002 F-350, 7.3 liter automatic, that I purchased a couple years ago. I have pulled/hauled light loads with it fine. I recently started to pull a 5th wheel (approx 10,000 Lbs). Pulling uphill (approx 2400-2500 RPM) I have heard a metalic tapping sound that speeds up and slows down with the RPMs. It stops when not under uphill load. I have had it into the dealer and everything checks out. I was told this motor has a fan clutch that engages when the engine starts to warm up and that is what I'm hearing. Is this normal?
The truck has 125,000 miles on it. I plan on going on trip soon and don't want to have any problems.