I didn't have one when I did my diff drop, but I have a thunk as well. It is my ball joints I also think there is some front prop shaft noise, look at the angle that you have on that CV joint now, not pretty. I have ripped two sets of boots on the prop shaft at this point (not replaceable, I picked up a spare shaft at the yards) I have decided to leave it alone until it starts screaming, then swap again.