So I have been noticing a high pitched squeeling sound at low rpm's and idle after the truck has fully warmed up. Now its getting louder and more consistent, to the point it drives me nuts every time i stop at a light.

And I still have no idea where its coming from! Really sounds like it is coming from near the rail, or drivers side of the block just underneath. Went over everything with mechanics stethescope and still can't tell. I tried belt dressing and checked all the pullies/ fan hub when i recently changed the belt. I have been getting an P0483 fan speed code though....

Then I was thinking boost leak from manifold gasket or maybe fuel leaking past the rail relief valve but now I'm thinking it sounds like bearings going out? I was thinking maybe pilot bearing but the sound doesn't change when I engage/disengage clutch or put it in gear.

So what else could it be? Could you hear push rod bearings or camshaft bearings going out? Guess I better pull an oil sample hear soon and send it to the lab...

 

I had a simular noise and it ended up being the belt tensioner.