Do you mean E steps? The extruder steps per mm is the fourth value in the Marlin DEFAULT_AXIS_STEPS_PER_UNIT array of constants in the configuration.h source file.
Actually, if you think about it this can't be the reason for your troubles. Yes, the large gear seizing could cause the extrusion to stop, but it couldn't cause a notch in the filament. The gear seizing against the extruder body would simply bind up the motor, causing it to stop rotating or skip steps. For the filament to get notched, the large gear and hobbed bolt are likely rotating just fine.
Many of the possibilities for extrusion stopping have already been mentioned, but FWIW this post has my composite list based on what people have reported -
http://3dprintboard.com/showthread.p...ll=1#post58220