Ok, on our Rig. the Wheel Well Metal toward the front of the tire should be connected by 2 brackets to the fender shirt. They are L brackets that are epoxyed to the skirt. Ours had come loose. So it banged on adjacent metal.
There is a square piece of tubing that supports the step that is just in front of this wheel well metal. I went thru one of the brackets that should be attached to the fender skirt and drilled a hole in this square tubing that supports the step. I did not have to drill a hole in the bracket because it has a slot there already. I just had to drill into the square tubing. I then used a 1/4 inch bolt about 2 inches long with a fairly large fender type washer under the head of the bolt. Then the bolt goes into the square tubing. Is it very tricky but I used an open end wrench to hold the lock nut. I used masking tape to attach the nut to the open end of the wrench and then slip the wrench into the 1 inch tubing and thru trial and error got the bolt started into the nut. ThenI tightend the bolt securly using the wrench in the tubing to hold the nut. After this, you can hit on the fender well and it will not rattle.
I forgot to tell you that I had a 1 1/4 inch thick piece of hard black rubber that I drilled a 3/8 hole in and put it between the bracket and the tubing. If you need more explaination call me. 817 907 8047
38ft, 2004, Diesel