Just bought a 98 blazer 4x4 4.3 v6… rides and drives nice got on the highway and a loud whirring noise came on… got off and stopped for a while then it went away. Drove 20-40 mph all the way home and no noise. Definetly from front end. I found a YouTube video and this is what it sounds like EXACTLY. https://youtube.com/shorts/BCozijNzhfA?feature=share
hopefully posting links is allowed.. if not let me know. I’m thinking it’s the actuator for 4x4.. anybody have and idea based on the sound?

 

I get intermittent loudness I believe it is the fan sensing something and coming on extra hard. Not as loud as your noise though.

 

it’s definetly not the fan it gets louder the faster you go and slows down when you slow down..

 

Anyone have a clue??

 

I'll say that from the sounds of it, you are on the right track concerning the front axle engagement system (actuator or possibly deeper in the front axle). There are a few tech articles that might help in the Tech Article (DIY) section. Check the index and read through a few.