I have a video of what it sounds like here please let me know what you think it is and how to fix it. Thanks in advance.

 

Dang, that thing sounds like an airplane is about to land on your blazer. A bearing could have went bad somewhere. Are you noticing any voltage drops?

Edit: In the video, something doesn't look right about the idler pulley. And check to see that the belt tensioner isn't rocking. Eliminating things could narrow down your possibilities. That's how I think of it.

 

take the belt off and see if it still does it. If it doesnt with the belt off then start spinning pulleys by hand. One should make some noise, I'm with Tibby, the idler pulley looks off.

 

sounds like the alternator to me

 

take off the belt and turn everything by hand that you can
You should be able to feel something gritty
BTW you wont be able to turn the crank by hand ,JIK you dont know any better

 

alternator x2




all u can do is take belt off,and start it for only 30 secs or so cold. if noise is gone,cut car off and start spinning pulleys. if it makes a gritty noise,replace it. they should spin like butta.

 

alright I am seconds away from trying and will reply here shortly thanks for the tips

 

Ok so....
-still makes noise without belt on
-all things that spin are doing so like "butta"
-so nothing to do with anything that spins on belt.

I should also mention this noise started when I drove over my tire ramps to do an oil change.
could the power steering pump be doing this? the fluid is like almost nothing when I just checked.
maybe the fuel pump?

 

if steering pump is low,add fluid.

this might be a vacuum leak. Pick up some starter fluid,and while engine is running spray around the throttle body,intake etc and if idle changes while doing so,you found a leak.

 

if it was the power steering pump then it wouldn't make the noise with no belt. Check you vacuum lines, I had one make a noise similar to that when it got weak. It would collapse on itself and re-expand over and over again, looked like it was vibrating. also make sure a cooler line didnt get kinked. Follow the the sound of that noise.