Do you mean the slots in the outdrives are really large or the outdrives themselves are meant for a physically larger "ball end"? I ask because I've not seen a TT01 ball diff but know Stock TT01 bones are huge plastic things. If it's just that the slots that are too wide use some driveshaft protectors/blades/cushions/u-pieces. If the gap is 3.5mm you can use Tamiya ones such as 51536 swing shaft cap.