Improved four-wheel-drive off-road hydraulic transmission speed changer

The utility model discloses an improved four-wheel-drive cross-country hydraulic transmission speed changer which comprises a speed changing box body, a torque converter is fixed on the outer side of the speed changing box body, and a turbine shaft of the torque converter is connected with a first clutch shaft on the speed changing box body. A first clutch shaft, a second clutch shaft, a third clutch shaft, a first idler shaft, an axle release shaft, a front axle output shaft and a rear axle output shaft are arranged in the gearbox body; a first gear is fixed or formed on the first clutch shaft, a second gear and a third gear are movably connected to the first clutch shaft through bearings, and a seventh gear is fixed or formed on the second clutch shaft; power input by the turbine shaft is directly conveyed to the first coupler, speed reduction is not needed any more, and therefore working torque needed by the clutch is reduced, the number of friction plates and spacers of the clutch can be reduced, the size