RE: AMAZING TRACKED R/C
Turning the tread from one end like that, you are basically in the worst-case from a mechanical advantage point of view.
So you will need a great deal of torque to move the treads effectively like that, and to keep them in place when you don't want to move them. A worm gear assembly is probably your best bet. If you need to gear down farther, do it before the worm gear. If the last gear in your setup is a worm gear, any slop is very minimal.