mason dunlap

Hey guys! I finally got my first gmc just 2 days ago! It's a 2005 Sierra 1500. It's got 152k miles on it and drives pretty well! It has a drone that I thought was coming from the front so I'm thinking wheel bearing. It changes when I turn and I think I hear it coming from the front but my dad and brothers swear they hear it coming from the rear. Is there any way to check the rear bearings without tearing into the diff? It sounds like a low pitched dremel tool going off. The front hubs are pretty rusty so I'm sure they need replaced anyways. Any advice would be great before I go dumping $300 into parts.