Truck is a 2003 4x4 4.0L Edge

Hoping to get some help with a transmission issue. I am getting a very light bearing-like whine with truck stopped in neutral with clutch engaged and a more predominant whine while moving in 2nd and 4th gear only. Gears 1, 3, and 5 are completely silent. I have replaced transmission fluid with royal purple synchromax and it didn't change anything. Also have replaced transmission plug and ring and rechecked fluid levels to make sure there are no leaks. Whining noise does not change with RPM or acceleration/deceleration.

I have researched this on multiple forums extensively and haven't found anything that has given me an answer. Anyone have any ideas what could be wearing out?