Hey guys I bought an 04 GMC 2500 hd truck with the LB7 Duramax diesel about 11 months ago. She’s got 288K miles on her but for the deal I got I couldn’t pass it up. Since Ive had it Ive had no major issues except minor things like window motors going out, loose steering, etc. However the other day I was on the job and fired it up getting ready to leave. It started makings this god awful racket that sounded like a major electrical glitch coming from under the truck. It would do it both idling and driving. Didn’t seem to effect driving at all. It sporadically still does it yet I never have the time to pinpoint source of the noise. Earlier today it did it while I was pulling up to our hunting property. I had just enough time to slide under the truck to hear it sound like it was winding down then stopped again. This is out of my pay grade so do any of you fellas have clue what it is??