I have an 04 FX4 5.4 and it has developed a tapping sound like a lifter. It does not do it all the time and it does not do it when I start up the engine. After it has been running for a while it will start then it continues most of the time until I shut it down. I also have noticed it gets a little worse when I hook up my boat to it. Now, my boat is heavy, about 2,000 lbs, and I have to turn off the overdrive to keep it from constantly switching back and forth from drive to overdrive. When pulling the boat, like I said before the tapping sound is worse and gets even louder if I have to accelerate to pass another vehicle.... Has anyone had a similar experience? Does anyone have any ideas as to how to fix it?

 

Kind of sounds like a manifold leak but could be a number of things really