Is this kind of like the 2-speed it has?
Had to re-read your original post to remember... the LST had a similar 2 speed. If you held the 1st gear stationary with your hand, it would roll freely in one direction (forward I think), but rip the gear out of your hand in the other direction...
I have a similar issue figuring out how wankle engines transfer power and the "piston" rotates properly to do so... but that's another thread for another day. lol!
Do you know the brand/model of the car your having issues with? Can you post some clear photo's of the chassis with the body off...
I always put a bit of oil on mine, just light 3-in-1 or something similar. No grease though.
Strangely, in all the years of running nitro MT's, I think I only had one trans owb go bad on me. Quite a few engine owb's though. Guessing the higher rpm's and castor oil tend to take their toll on...