The damaged axle is the one going through the black 36 teeth gear and the green 20 teeth gear in the wheel assembly. The driver gear is a 12 teeth gear on the motor axle. The follower gear is the black 36 teeth gear. This increases the torque by a factor of 3. The stalled torque of the PF XL motor can reach 40 Ncm and thus the torque of the damaged axle can reach 120 Ncm.