The latest bleeding edge build lets you make gearboxes with as much reduction as you can make the space for. 1000:1 should be no problem if you stack three 10:1 gear sets.
I've posted the bot in case testing might help figure out what's wrong.
https://gametechmods.com/forums/robot-rumble-2-0/robot-rumble-2-0-robot-combat-s...