Yesterday my truck started to clunk while I was accelerating up to freeway speed. It only did it once and it came from the front end. I left for work this morning and noticed it again. It did it about once every 30sec or less. It does not do it when I am coasting and it is not related to road bumps. It is also not consistant as it happens at random times. The clunk sounds like metal on metal similar to the clunk that you get taking it in and out of 4wd. Any Ideas??? this is my work truck and if it dont work I dont work