PURPOSE: To conduct continuously variable transmission with simple constitution by inputting an output of a main power part via a bevel gear, a pair of transfer gears and the like, by providing a pair of hydraulic systems comprising hydraulic motors and a hydraulic pumps, and by combining paired satellite gears to each hydraulic system.

CONSTITUTION: This hydromechanical steering transmission has an input driving gear train 10, and this transmits an output of a main power part. 12 to a pair of transfer gears 18 via a bevel gear 14 and a shaft 16 to rotate sleeve shafts 22, 28 via gears 20, 26 meshed with the respective gears 18. Hydraulic systems 24, 30 comprising hydraulic pumps A1, A2 and hydraulic motors B1, B2 are connected to the shafts 22, 28, and the respective hydraulic systems 24, 30 generate in its shafts 32, 34 hydraulic outputs variable in a speed range from an advancing full speed to a retreating full speed. The hydraulic systems 24, 30 constitute a range switching mechanism 52, and the mechanism 52 is further provided the first and second paired satellite gears 54, 56.