Ultralite diff cases

[suicideneil]

That's your problem really- the rpms are too low so you have to use insnaely high gearing in order to get some decent wheel speed. You would be far better off with the 2200kv 1515 motor on 4s lipo, or an 1800kv 1518 motor if you can find one; the 1717 motor is really for 1/5 scale or heavy MTs on 6s lipo- you need the rpms...