Humming noise when backing off the throttle. What could it be?

[UtahOverland]

Humming noise when backing off the throttle. What could it be?

 

[UKlandy]

Could be many issues but I would say it is something related with the Diff

 

[Dirt lover]

Diff or transmission, it can be either. It can also be something very simple though. Just take it to a mechanic to be sure it is hard to tell through here