When slowing to a stop in my BJ73 FRP cruiser I get a loud vibration sound (imagine a nuclear reactor powering down in a cheap movie

The hubs are set to Free, 4wd switch is not engaged and 4wd light is off. 4wd is working fine aswell.
Does anyone else have this problem?
Hub bearings?
Transfercase?
Auto?
Diff's?
Diff oil?
Prop shaft?
Any help to narrow it down would be appreciated.