Abstract: Rear axle hypoid pinion and ring gears made of bainitic nodular iron with shell moulded cast teeth have successfully been used on light and medium trucks in China for several years. Cu and Mo alloyed iron with low Mn and high Si, good inoculation, graphite nodule refinement, and ,correct austempering technology result in complete transformaticn to fine grain .lower bainitic structure with high mechanical properties. Shot-peening raises the bending endurance limit of the .gear teeth. Optimum modification of tooth parameters of pattern-gears, 3-points pitch circle positioning in machining and electric spark running-in ensure good meshing of tooth flanks, quiet running and long life of gears. Road reliability tests of 25000 and 50000 KM and several years ,of actual service on more than ten types of trucks have proved that gears thus made are satisfactory for the duty. Production by this method saves labour and time, and does not need large investment in equipments. Such gears are now in batch-production in China.