Dreaded clunk when turning

Some good pointers there. Remove fill plug before you re-assemble diff. In case its stuck, if you have to drill it out its easier. My gmc pickup fill plug is stuck from some gorilla tightening it.
Didnt realize until i had cover sealed up. So i put 1-3/4 bottles of gear oil in through vent. Next time. Since then i check plug before i pull covers.