Abstract: The invention consists of an engine driving a wet clutch and hydrostatic pump and connected hydrostatic motor. The output of the motor drives the sun gear of a hydro-mechanical planetary drive and the output of the clutch drives the ring gear of the same drive. The carrier is the output and drives the rotors of an agricultural combine. The transmission is controlled by a microcomputer. The microcomputer receives signals from an engine speed sensor and a rotor speed sensor and transmits controlling signals to the hydrostatic pump's swash plate and to a clutch valve allowing a quantity of hydraulic fluid to enter the clutch. The microcomputer can also send a signal to brake the ring gear while reversing the direction of the hydrostatic pump motor to allow act as a reverser for the rotor. The microcomputer also can receive signals from the rotor speed sensor to open the clutch valve allowing a quantity of hydraulic fluid to enter and synchronize the clutch.