so this noise will only happen at around 2000rpms and up it is driving me crazy that i cant figure it out and not able to pull anything with my excursion

 

what motor is in the truck? i've heard turbo whine sorta like that and i've had a 6.7 with an exhaust manifold gaskets leaking on the driver side that sounded just like that.

 

It's the 7.3L I took by a place and they took the belt off and power stalled it and it didn't make the noise then it made the noise with the belt on. That's what was weird

 

If you took the belt off and it didn't make the noise maybe it is the tensioner. They are known to go bad. It is an inexpensive part anyway and not that hard to replace.

 

Wouldn't the pulley be stiff. cuz I took the belt off to change it thinking the belt was too loose and might b slipping and all the pulleys spun with ease

 

The bearing could still spin freely but be worn or dry,when you put tension on it with the belt it could cause it to squeal. Try spraying some WD-40 in the bearing to see if it stops,this is not a fix just a way to see if it may be the cause.

 

Their suppose to be a certain tension on a belt tensioner too loose then a pulley can just spin on the belt and make a henderndous noise...