A hydraulic mechanical transmission includes a first hydraulic unit having a first shaft and a second hydraulic unit having a second shaft. The second hydraulic unit is connected in hydraulic fluid communication with the first hydraulic unit by high and low pressure lines. At least one of the first and second hydraulic units has variable displacement. A mechanical torque transfer arrangement transfers torque between the first shaft and the rotatable component of the second hydraulic unit. One of the first and second hydraulic units operates as a hydraulic pump and the other of the first and second hydraulic units operates as a hydraulic motor.