Successful conversion of nodular iron hypoid gears from steel to nodular iron required initial vehicle and laboratory fatigue tests to supplement a material development program. This was followed by manufacturing process refinement and finally an extensive series of vehicle durability tests. Nodular iron gears have good fatigue life, are approximately 10% lighter than steel, have greater damping capacity which reduces noise, have greater torsional strength and the graphite in nodular iron results in more score resistance. Nodular iron gears have significantly improved machinability which translates to improved productivity. They are easier to heat treat, can be “free-quenched”, and require less energy to manufacture.
