501 needs your help – P60k 256:1 Banebots Transmission

[MrForbes]

Another approach might be to use a gearbox with less reduction, and add a stage of chain or belt and sprockets. Might require redesign of stuff that's kind of hard to do at this point in time.

Small shafts with lots of torque on them are asking for trouble....

[AdamHeard]

I strongly advise you start working on another solution now, while you have the time to implement change effectively.

Merely replacing the gearbox will just get you a few more hours of runtime.