Originally Posted by Besercoe

Are you sanding the ring out of them completely?
If so, and you have replaced the thrust washer, then you only have one more part that moves, is to replace the 3mm balls.

Also, when installing the thrust washer, i always put the side where the brass insert is more chamfered, against the screw head, this seems to make a big difference on the smoothness of the diff (not as much on a 416, but on older diffs with the smaller diff screw it made a massive difference)