The clunking makes me think the problem is likely the mount for the front of the differential. when the rubber sandwiched between the metal plates finally gives up it exhibits symptoms just like you are describing.
You said everything visually looks good in the rear, did you try prying on/ jacking up the nose of the diff? it often separates where the rubber is glued to the metal and therefore looks fine without further probing. it takes considerable force to move it up and down even fully separated.