Rear drive vehicles transfer power to the rear wheels through the Gear Carrier Assembly, which is fit at the central section of the Rear Axle. The Gear Carrier Assembly includes hypoid ring and pinion gears, set at the heart of the system. However, gear scoring and whine noise frequently emerge as critical challenges, leading to reduced durability and compromised performance of the vehicle. This study focuses on the design and process improvements aimed at addressing these concerns while enhancing the overall performance and reliability of hypoid gears.
Design enhancements include macro geometry refinements, material upgrades, and modifications in the heat treatment process. These changes improved key mechanical properties such as contact stress, bending strength, impact strength, and motion transmission error (MTE). Process optimizations involved precise control over carburizing, hardening, and quenching temperatures, as well as adjustments in quenching pressure. These measures improved core and case hardness as well as microstructure quality. Additionally, post – lapping, finishing techniques such as vibro deburring and manganese phosphating were introduced to achieve gear surface qualities comparable to ground gears.
The results demonstrated significant advancements, including reduced MTE, improved contact patterns transitioning from centre-biased to diagonal-biased, lower drivetrain losses, enhanced NVH characteristics, and increased durability. Critical concerns such as furnace variation, case depth and core hardness inconsistencies, pinion straightening rejections, and vibro finishing process inefficiencies were identified and addressed during the development.
This paper provides comprehensive steps adopted for improving hypoid gear performance, focusing on resolving scoring and noise challenges while achieving enhanced gear reliability and drivetrain efficiency.