2009 tacoma 4 door 4×4

I have noticing a slight vibration or grinding while driving at speeds of 55 to 60 mph , when I turn one way it goes away but I recently rotated tires and it's still there ... truck is lined up and I just can't figure it out ! I checked wheel bearings and they r fine , someone said my 4 wheel drive may not be fully disengaged ... please someone help !!!!

 

First off, welcome to TW! Second, this should probably be in 2nd gen discussion or somewhere. Once you post in the right place, you'll definitely get the help you need.