I will try and explain this as best as I can...

When the truck is cold and I start it I always let it warm up for a few minutes as a general rule. Lately I have been hearing a noise when I accelerate while the transmission is in drive. It only happens when I am in drive and will stop after a few minutes. Today I was at a stop light and depressed the brake while applying the accelerator, the noise was there. When I am in park I try to re-create the sound, no dice...

It kinda sounds like a cross between a hole in the exhaust headder and a loose/vibrating shield.

Any thoughts or suggestions would be greatly appreciated.

 

roll under there when its warm and get a trusted buddy to do the same thing and look around, sounds like you gots a rattle from something when the engine has torque put to it, should be easy to find.

 

Yeah, you have your engine torquing over and something is hitting under acceleration or doing the power brake, thing. You could possibly have loose or worn motor mounts or tranny mount. Get underneath and try to wiggle stuff, first.

 

Youd think that it would continue and not go away after a few minutes...it does come back after I shut it down for a little bit then start up to drive again.