TH350 Sprag & Steel Drum Assembly

The TH350 Sprag & Steel Drum Assembly by TCI is an essential internal transmission component engineered for TH350 automatic transmissions undergoing rebuild or performance upgrade. This assembly serves as the primary holding element within the transmission's planetary gearset, controlling directional power flow and preventing unwanted gear rollback during deceleration and neutral coast conditions. Whether you're rebuilding a tired stock transmission or upgrading a classic muscle car or street rod, this sprag and drum combination is critical to achieving reliable shift quality and long-term durability.

The TH350 Sprag & Steel Drum Assembly uses a precision one-way sprag clutch mechanism integrated with a heavy-duty steel drum to manage torque transmission and prevent reverse rotation of the intermediate planetary carrier. The sprag's cam-and-roller design engages instantly under load and freewheels smoothly during overrunning conditions, reducing parasitic drag and heat generation. TCI manufactures this assembly to exacting tolerances, ensuring proper engagement fit and compatibility with OEM and performance-level internal components. The steel drum construction provides superior fatigue resistance compared to cast alternatives, making it ideal for high-performance applications including street racing, towing, and sustained highway driving.

This sprag and drum assembly is essential for anyone performing a complete TH350 transmission rebuild—whether for stock restoration, torque converter upgrade projects, or serious performance modifications. Installation requires partial or complete transmission disassembly and should be paired with a full gasket and seal kit, friction and steel plates, and a quality rebuild manual specific to your application. Proper alignment during installation is critical to avoid sprag hang-up or premature wear. Weighing 10.1 lbs and engineered to OEM specifications, the TCI TH350 Sprag & Steel Drum Assembly delivers the reliability and shift consistency that experienced builders and transmission shops trust for street, strip, and restoration projects.