I rebuilt the ball diff last night. What a horribly designed pos. The diff rings need to be larger in diameter so they can go closer to the edge of the gear. It you run the diff balls on the outers holes, the edge of the diff rings is right at the centerline of the diff balls which is horrible. Since the diff isn't sealed off from the outside any little bit of dust, dirt, and grit can get into there and into the diff. I cleaned mine thoroughly and then carefully sanded the diff rings flat on 600 and then 1000 grit sandpaper, cleaned the diff balls clean, and then installed only 6 of them using only the inside holes. A small dab of black Associated black grease was used in each hole before the balls were installed. It is much smoother now. It will still probably get gritty but right now it's quite nice. I want to find a way to completely seal off the gears into their own box. Not having one in my opinion is a huge design flaw.