Axle bearings??

My 7 1/4” diff makes a rumbling sound. It’s not too loud, but slowly gets louder as speed increases. I don’t think it’s coming from the center, but who knows for sure. Seems smart to change out the axle bearings and proceed from there. Thoughts? 1970 Duster, 7 1/4 diff, never been touched other than me changing fluid a year or so ago.