will always happen when i drive, theres no way to drive without hearing it. now the weird thing is that it will rattle for awhile until it does a really quick loud rattle and makes the check engine light come on. once the check engine light comes on the rattling will completely stop. i tested this on a long road trip. the rattling wont start again until i completely shut my truck off. once i start driving again, the rattling will come back until it does that really quick and loud rattle and the check engine light comes on. this has been an on-going problem and is just getting worse. 