I have a '91 Blazer. Works pretty well, except for a loud humming that gets louder with increased vehicle speed. It has slowly gotten worse over the last year or more. It gets pretty loud at highway speed. It sounds like I have snow tires but I don't and it didn't used to sound like this. If I push in the clutch pedal or put it in neutral, it makes no difference. I did notice yesterday as I was driving 60mph or so and as the highway veered left that the hum went away while on that turn then went back to normal on the straightaway. I tried changing lanes to see if that shorter steering to the left made it go away. It didn't.
I'm guessing a bearing of some sort. Any advice out there?

 

Sounds like a bearing to me too.

You didn't say if it was 4wd or not.

Sounds like it is time to put it up on jack stands and try to find if you have any play in your wheel bearings or not. You will need to check front and back irrespective of it being 4wd or not.

 

It is 4WD.
My dad had a Blazer that had humming that had something to do with 4WD. Turning the 4WD on for a little bit then turning it off, made his stop temporarily. That doesn't work on mine. No mechanic was able to figure his out.
Thanks for the advice! I'll give that try