Larger pulleys are fine, but you need to adapt the centre pulleys to spec racing requirements otherwise you're killing your market share. I for one hate intergalactic size pinions and 64 pitch is not always feasible for outdoor tracks.
I have managed to adapt Kawada center pulleys (the largest I've got - 24 tooth) for use in some for my older cars (TA05R is one) but newer cars (Tamiya, Yokomo do not allow this move because the top deck is in the way.
Back to diff internal gears, it's all in the pitch used. It can be done, but costly. Real cars use straight cut satellites/planetary and they are notchy as well. Cutting (moulding) a better tooth profile becomes very involved the more precise you want to get. Don't know how they do it in printers and other applications, but it can be done. I have found in some older machinnery some really nice spiral bevel gears (too big for our diffs), but I have no idea how much they would cost to manufacture. This was out of an old punch card reader. Who said innovation was a new imperative?
Last edited by niznai; 10-20-2014 at 01:40 AM.