The 4th speed gear on the input shaft is used for not only 4th speed but also 6th speed by meshing with 6th speed gear on the output shaft #2. That is, the 4th speed gear is shared by two output shafts.

In case of M6GF2 model, this gear is shared by 4th speed (OP#2) and 2nd speed (OP#1) respectively.

Note that 3rd, 4th and 5th speed gear on the input shaft have been fitted by thermal pressing method (referred to as ‘interference fitting’) so that it is required to apply heat when overhaul the gear from the shaft.