I have a similar problem on my Disco. I removed the front DC DS for a few days and drove around, same problem. I think the problem is not the diff but within the TC.
Mike H might be able to help us since he's the TC guru
I've got about 1/4 turn of play and a clonk when accelerating and decelarating.
I just finished installing a brand new 30 degree wide yoke DC DS and same problem, so I guess it's time for a new TC.