Please help diagnose my front end noise

I have been reading threads in the forum regarding wheel bearing and front diff needle bearing noise but I'd like to ask for help before I order parts. (I try to do all my own repairs)

I have 140K on my 2008 Access Cab 4L V6. I'm hearing a noise from the front end that's gotten gradually louder over the past few weeks. The noise starts out as a very low frequency hum and the pitch gets higher as I go faster. It's most noticeable at about 35 MPH.

Putting the truck in 4WD-Low doesn't seem to make the sound go away as the threads about the needle bearing issue say it shroud.

I've noticed that at highway speeds anything more than a gentle curve to the right make the noise go away.

So - differential needle bearing or wheel bearing?

 

Left wheel bearing