I tried both 48 and 64. 48p asks for 6 balls (small diff), 64p asks for 8 balls.
As to type of balls, really doesnt matter for starter to mid level racers, the majority of "feeling" you got from the diff is from the diff bearing. Change the diff bearing more frequently seems to be the best solution.
If you must, source for a diff hub that carries 2 diff bearings. I used to have one, and share a tab bit of side load resulting from crashing, but otherwise useless for side load originating only from the diff pressure ring. It was made by shooters (sometimes aka sFooters), as far as i have heard they have stopped production. So if you see any stock, consider getting one. It was a very sincere aftermarket parts producer, very accurate cutting, good materials, too bad that if they really stopped manufacturing.
There are other suggestions, like using a bigger diff, or sanding your diff ring so that you dun need a tight diff (and high side load). Personally, never tried these, so i would not comment. Sharing of genuine experience is VERY MUCH APPRECIATED!
