[67Man]

I just bought my first Ford, a 67 Mustang for $600.00. I couldn't pass it up. While I was driving it home I heard a whine coming from the rearend. I can't tell if it is the gears or the bearings, it's not the pads. I know little about Fords and was wondering if there is a common weak point in that era of rearends? Any help is appreciated!