<p>The automotive drivetrain is a critical component for power transmission in vehicles, and its importance is self-evident. It is responsible for efficiently and smoothly transferring engine power to the wheels, directly affecting the vehicle’s acceleration performance, driving stability, and safety; it is an indispensable component for ensuring normal vehicle operation. Among these components, the transmission is a key part of the automotive drivetrain. However, metal failure currently occurs in vehicle transmissions, which directly affects the vehicle’s service life and performance. Shot peening is a cold-working surface-hardening process that uses high-speed shots to impact the surface of the material, causing plastic deformation and generating residual compressive stress, thereby enhancing the component’s fatigue strength. To better elucidate the influence of shot peening on the performance of vehicle transmission gears, this paper reviews recent phenomena and mechanisms of gear failure, introduces several novel shot peening techniques, analyzes the effects of different shot peening parameters on residual stresses, and focuses on investigating the mechanism by which residual stresses affect the high-cycle fatigue life of gears under bending load (pulsating cycle) conditions. Finally, the paper discusses methods for inspecting metal surface integrity. This paper provides a theoretical basis for future research on extending the service life of automotive transmission gears.</p>