Whine in Front End

Suburban now has 195K on it. About a week ago, it started making a whining noise in the front of the vehicle (while driving in 2wd) similar to the noise it usually makes when the 4wd is engaged. I thought I had lost the transfer case motor or the front actuator, but I checked both and they are engaging/disengaging fine. (I even jacked up the front end and confirmed this as well.) Had a bad left differential seal and left CV axle, so I had them replaced, but the whine is still there. Tires are older, but not worn abnormally.

It changes pitch with road speed, not engine speed. I also checked wheel bearings, but they are good. Seems to be coming from the front differential or thereabouts.

What would be the most likely culprit of this particular noise?

Thank you!