trying to eliminate possibilities. I have a consistent sound from the rear of the truck. Almost sure it is new tires but want to eliminate other things. If the sound stays they same while coasting in neutral - does that eliminate the pinion bearing in differential or does the drive shaft still rotate? Will check wheel bearing by pulling on tires over weekend. Sound showed up with new tires but the wild card was the old tires were so noisy it could have been there all along.
Have 190K miles

When my pinion bearing went, I could move pinion up and down slightly. Put it in neutral when you check pinion movement. Also jack the rear, chock other wheels. Start it up and bring speed up so the drivetrain is spinning but tires not hitting ground. Actually you just need to jack the drive tire, the other one can stay on ground. Good way to pinpoint drivetrain noise.

For some reason I cringe every time someone suggests a Ferris Bueler. Not that I have personal experience.

Pinion noise tends to change with changes from under power, coasting in neutral, and engine breaking.

Wheel bearing noise may or may not be consistent through the 3 above mentioned loading scenarios. It may change while cornering, or braking. It tends to be one side or the other.

You could also have failing u-joint(s). You can hand test and/or pump in grease and see if that provides temporary relief.

If your tires are spinning, so should your driveline for the rear.

these types of things are hard to find sometimes.

last fall I replaced the bearings in my 3rd member, front/rear pinion and carrier both sides. reset the backlash and got the pattern acceptable. 230K on that 3rd member.

after I did this and nothing exploded and or melted... the new bearings made my 3rd member much quieter. I was surprised how much quieter. the old bearings and races were not really in terrible condition but they were scored a bit and it was making them very noisy.

if it's constant noise that does not change much except with speed, it's probably just older bearing noise.

I have had a pinion go bad and it's super noticeable, I have had wheel bearings go bad also very obvious. if it's subtle I would suggest maybe a fluid change in the rear to see if it quiets it down a bit, if it does? prob just older bearings and maybe some sand/dirt/water got in there at one point. it happens.