The heavy duty NV4500 manual transmission is designed for a torque capacity of 610 N-m, 10% more than the standard duty version. A larger diameter mainshaft and matching overdrive gear, a larger diameter input shaft and a strengthened case were required to provide the higher torque capacity. Input and output splines and a speedometer drive gear were designed to meet customer requirements. A customer-required shift lever for this transmission was made compatible with the standard duty version. A two-wheel drive extension and a four wheel drive transfer case adapter were also developed to customer requirements.