Jdgriff

A couple weeks ago I get this humming noise underneath my vehicle sounds like the transfer case the oil is fine ,but it's between the transfer case and transmission making the noise jacked up the truck doesn't do it in first gear a little and second gear and drive does it all the time . When driving on the road at 50 miles an hour if I keep the the throttle consistent it doesn't make the noise but when I decelerate it does wondering if this is a transmission problem or a transfer case problem I can't find a thing thank you. have video but site does not let me download