This is the aft transmission. It takes power input from the combining transmission and reduces drive shaft rotation speed to 225 RPM. It then transfers that power to the aft rotor system.

This is an engine transmission. It transfers the power from the N2/NP power turbine section of the engine and slightly reduces the RPM. This power is sent to the combining transmission. There are two engines each requiring their own engine transmission.

This is the forward transmission. It recieves power inputs from the combining transmission and, similar to the aft transmission, reduces driveshaft speed to 225 RPM. Then transfers the power to forward rotor system.

This is the combining transmission. It has two power inputs, one from each engine transmission. There are also two power outputs, one to the forward transmission and the other to the aft transmission. It also reduces the engine transmission driveshaft RPM by approximately 20:1.