When I first accelerate when I am in 2 wheel drive I am hearing a slight clunk noise comming from the rear end. I took the truck too a mechanic and was told it is the rear end noise is just the rearend spooling up and the noise is normal. There were several things that we figured it wasn't. It's not the brake drum shifting from the breaks, not a U joints, not the rear leaf spring either. The Noise is not normal i don't think. it's a metal "clang" noise. Can anyone help?