while accelerating there is a whrrring/howling sound comming from under the hood. I havent a clue what it could be.
2005 LLY 2500HD with 140000 kms

Maybe its a pulley bearing, you better pull the belt and spin them all.

pulley bearings seem fine. but i noticed the noise is associated with smoke comming from the exhaust. the weirdest part is the noise will stop just as fast as it starts

does it happen when your building boost, or at anytime?

i hear a weird noise in my 05 too. Its not associated with the engine or anything mechanical at all. My noise begins at speeds as low as 45 mph and can be intermittent or constant at higher speeds. However, the noise only happens during the summer or any time the temp is 90 or above.... The sound is like a higher pitched tuning fork

Sure its not just your fan engaging?

i believe it is while building boost. but it will randomly stop making the noise while still accelerating

mine did this exact same thing a month ago or so, It was my egr blocking plate leaking. I took out the plate, covered both sides with gasket maker and put it back in and has been silent ever since. Even if you dont have a blocker plate, it might be worth taking the place you put blocker plate and replacing the gasket, its cheap.

I have a high pitched diesel sound from a stoplight and towing. I call it a chirping like a sports whistle but sounds like traditional diesel clatter. Goes away at 5 MPH, No noises without the trailer. Sounds nothing like a belt or A/C moan.

My old man had a similar issue while he was out of town last week. Loud screeching sound while under boost only, we thought it was his EGR. He got back and took the truck for a drive. Here is the best part he was a helicopter pilot and recognized the sound immediately. Pulled over lifted the back seat and move a bunch of tools he had from under the seat. Turns out one of the tools was vibrating on a screw which was wedged by the seat. This essentially made a tuning fork with the chassy. My brother and I could not believe it when the noise stopped after he moved his tools. We would have never found this noise as it sounded nothing like vibrating tools and was extremely loud on the passenger side of the truck and again only when under boost.

Turns out this used to happen in helicopters all the time.

This may not be your issue but worth a shot.

Hell, with some noises, it can be something totally different than what you think.