The main function of Chongqing GC series gearbox is to reduce speed and bear propeller thrust. Adjustable propellers are configured for medium and large ships for power propulsion, and the positive and negative pitch of the adjustable propeller is used to achieve forward and reverse functions. There are two structural forms: vertically offset and horizontally offset.

The two forms of GC series have 13 specifications each according to the center distance, with a total of 26 models.