Refer to figure.
The Main Gearbox (Accessory Gearbox) transmits the drive through epicyclic gearing to the Main Rotor Shaft. The Gearbox also provides drive for the tail rotor, generators, alternators, hydraulic and oil pumps, oil coolers and tachometers.

The Gearbox housing is normally light alloy castings with steel liners in the bearing recesses and steel inserts for the threads. It is usually bolted to the airframe at the base and is supported by A-frames or struts. The Main Gearbox is pressure lubricated by a spur gear oil pump and the oil is cooled in a radiator matrix through which air is forced by the oil cooler fan.

The hydraulic pump of the control system is driven by the Main Rotor Gearbox.