Loose spider gears
Been in quite a few of these, they clunked from new. There should be next to nothing in slack on the spiders. Excessive wheel spin burns the thrust washers and cross pins. My guess it the cross pin is worn. Deal with it before it tries to cut the case in half. Way cheaper now then after it goes boom! Dont have the specs handy, but when i was setting crown and pinion, i always went on the low side of backlash. I prefer the corporate diffs as they are so easy to dial in.