The flapping sound is coming from under my L. It starts at 65mph. I've had it to the dealer and they can't find it either.To me it sounds wind related. It won't do it standing still / engine running at any rpm. The sound does not speed up or slow down with the speed of the truck.We've looked under on the hoist, nothing seems lose.............Has anyone had this problem......help please

 

Look at the rubber peice between the bumper and the frame right under the intercooler radiator...

Doug

 

Are you sure it's from under the truck? The 01-02s are notorious for the top rubber trim over the windsheild coming off, and it flaps as you're going down the road. I'd go out to the truck and take a quick look at that. Ours flew off at 125mph. Though I threw the blower belt because I saw it go flying out the back of the truck. Took about twenty minutes to figure what exactly came off the truck .

 

My 2000 doae it also. The rubber windshield seal just above the mirror outside, used to come loose regularly. A little dab of silicone in a few spots holds it nicely in place now

 

If you do a little searching, you will see that there are a few of us who had the same problem. I too had that flapping noise awhile back. It happened when I was under WOT above 60mph. I had the SVT tech at my dealership take it out with me. He traced it to a bad muffler. Something let go inside. It sounded like a wet rag flapping in the wind. Haven't had it happen since then.. Just a thought..

 

Check this too....

I had a flapping sound over 60 mph and it turned out to be the paper material used between the door panel and the door. I took the panel off and low and behold, one side had come up so I just pushed it back down. Problem solved.