i have a similar problem ive had a new rearend trans and transfercase done on my 02 blazer ive herad this noise a few times now it only happens when doingabout 75 80 mph i start hearing a whining noise almost like a supercharger mixed with a metal on metal screaching noise
when i slow down it gets louder and the tone gets deeper as it decrases in speed i getto about 15 mph hit the 4hi button and it goes clunk into 4wd and the noise goes away what the hell is up with this ive also noticed that when in 2wd my front driveshaft spins while moving (is this normal) ive heard people say yes but i work at an instant lube and have the chance tosee underneath vechiles while thererolling and ive seen the same truck as mines (more than one) and when they roll out the front shatf isnt turning ihavent had all these problems since the new transfer was put in