Note:
To find the correct Main Drive Shaft, look at the position of the key seat on the shaft relative to the large hole in the gear.
If this is exactly opposite you will need the GSX Main Drive Shaft (Tower Down) 47-075485-003.
If this is slightly offset to the right (2 teeth of the gear) you will need the shaft for the older machine types 47-072063-003 (non Tower Down).