Heat Treatment and Manufacturing Variability in Gearbox NVH : An Evidence‐Aware Critical Review and Validation‐Oriented Modeling Roadmap

ABSTRACT

Gear whine arises from mesh excitation, structural transfer paths, and acoustic radiation. Heat treatment and manufacturing determine the final tooth geometry, residual‐stress state, surface integrity, hardness profile, and unit‐to‐unit variability entering this chain. This structured critical review maps evidence linking phase transformation, heat‐treatment distortion, retained austenite, finishing, material damping, manufacturing scatter, and nonuniform wear of case‐hardened tooth flanks to transmission error (TE), vibration, and noise. Direct NVH evidence is distinguished from indirect evidence based on material state, geometry, durability, or modal behavior. The strongest evidence supports a process and finishing → final measured geometry and surface state → static or dynamic TE and dynamic force → structural response → sound pathway, whereas direct phase‐fraction or hardness‐to‐noise links in conventional case‐hardened steel remain weak. The review applies explicit source‐prioritization criteria and distinguishes representative evidence mapping from exhaustive systematic screening. An evidence‐derived modeling and validation roadmap is presented as a literature synthesis rather than a separately validated all‐in‐one model: final measured geometry is the baseline input, while thermometallurgical and wear‐evolution modules are activated only when their effects are independently characterized. The review additionally translates manufacturing variability into process‐capability‐informed geometric dimensioning and tolerancing (GD&T) for noise‐sensitive design.