My son's D1 just developed a loud rattle yesterday from under the truck. Not a knock or tick - but a loud rattle. Not sure if it is one of the cats or something else. It doesn't sound like it's coming from the engine. It seems to lessen when the engine RPMs are increased. I am not sure what the issue is and can't look at it until this weekend because of my job. He is not driving it until we find the issue, just wanted to get some sage advice that D-WEB is known for before I look at it.