Humming noise coming from the middle of the drive shaft and transfer case

I have a 2021 Tacoma 2wd and I am hearing a humming noise coming from the transfer case and from the drive shaft. I need help finding what it could be.

 

To my knowledge a 2wd does not have a transfer case.

When is this noise produced?

The only thing I can possibly help with is that lots of people report a noise long after the truck has been turned off (like for hours) and it is the evaporator system doing a test, that noise seems to be from the gas tank area. I personally have not yet encountered the test.