compute the maximum resisting torque that can be overcome by the system at the shaft axis

As Yaniv Ben David states this post needs some clarification. Add a sketch and some more information.

Assuming "shaft axis" is the output shaft and the transmission goes from fast at motor shaft to slow at output shaft the maximum torque is:

$ T_{out,max} = i cdot T_{mot,max} = 32 Nm dots 36 Nm $ for 'typical' electric motors at low speed.

Considering a rough estimate 10% losses in the drive train, this means you get approx. 29 Nm of torque on the output shaft.