I have an 87 f250 4x4 6.9 with ATS turbo. I have been getting a strange noise once in awhile that has me baffled. The truck runs fine everything works but some times when I shut it off and start to walk away I get a loud bang noise as if something that has been stuck is letting go. Seems to be coming from the front of the truck or maybe the trans area. It just started doing it in the last day or so. When I stop I let it run for a few seconds and check the EGT to see if it is somewhat cool before I shut it off. Other than cleaning up some trailer wiring I have not done anything out of the ordinary to it lately. Any one have any ideas. Keith