Abstract: A heavy duty hydromechanical transmission adapted for agricultural and industrial type tractors and for heavy duty construction type vehicles as well as line haul tractors is disclosed. The transmission utilizes an input shaft which is driven by a power source and drives dual planetary gear sets. These planetary gear assemblies are each geared to two separate variable displacement hydrostatic pump and/or motor units which are arranged in a closed hydrostatic fluid flow circuit. Each planetary gear set also drives a countershaft which is utilized as part of a multispeed transmission. The hydrostatic units are used as variable displacement pumps or motors to obtain smooth starting and to eliminate the need for a conventional master clutch normally used for starting a vehicle or for shifting gears. These units are also used to provide the high-starting torque through hydraulic torque regeneration.