I had a similar sound and it was the driveshaft center bearing.

If you are reversing and you hear that sound that's kind of the giveaway of the shaft vs a wheel bearing.

Also if you think about the revolutions of the driveshaft vs the wheels, that's why it sounds "fast" when you're moving slowly.

In my case accelerating or loading the drivetrain made the noise go away for a while and then it changed to different howls and squeaks as I kept driving it