Add possibly replacing the spur gear if the balls get too hot from slipping and enlarge the holes.

Just like any other ball diff, the C-Diff does need maintenance. It would be worth the effort to pull it apart clean & relube and reassemble to make sure it is correct.
Black grease on the thrust and clear diff grease on the balls.

Here's a walk through.
http://www.rctech.net/forum/10600508-post878.html