2008 2wd whine

Hello everyone,
Have a 2008 2wd 4runner with 231500 on the odo.
I have a weird whine/vibration.
I can feel it in the floorboard, sounds like it is coming from the rear end.
I will say it is quieter when going right around corners.
It starts at about 15mph, goes away above 70mph. I also can put it in neutral and sound is still there. Sound also changes with rpms.
I have had it on jack stands, and with it on the stands I can still hear it in the 20-30mph range.
I dont have any play in any of the wheels at all.
There is ever so slight side to side play in the drive shaft. I dont know if that is an issue, but there is no front to back play at all.

Thinking will check diff fluids first, then go to u joints, and then wheel bearings. I dont really want to just throw money at it blindly.

Anyone have any other thought? I picked this up in August for a good price and I could hear it then but thought it might be the tires just humming. It is in great shape overall for the age, and was a 1 owner...40+ year old woman so wasnt driven hard. Has a spotless...and meticulous carfax record.

Thanks!