Speedo Driven Gear GM 39 Tooth Brown

The TCI Speedo Driven Gear GM 39 Tooth Brown is a precision speedometer drive gear engineered for General Motors automatic transmissions. This 39-tooth plastic component is the driven half of the speedometer drive assembly, responsible for translating transmission output shaft rotation into accurate speed readings on the instrument cluster. The brown color distinguishes it from other tooth-count variants in the TCI lineup and ensures proper identification during installation and troubleshooting.

This gear is OEM-compatible with GM 200C, 375B, TH425, TH475, and 700R4 transmissions—a broad range of mid-to-late-model GM passenger vehicles. The 39-tooth configuration is a standard ratio that compensates for tire diameter and rear-axle gear ratio to deliver calibrated speedometer accuracy. As a driven gear, it meshes with the speedometer drive gear (typically 16 or 17 teeth depending on application) to reduce rotational speed before it enters the speedometer cable. The plastic construction is appropriate for this low-torque, high-speed application and minimizes wear on the drive gear.

This component is essential for restorers, transmission rebuilders, and technicians performing transmission repairs or swaps on GM vehicles from the late 1960s through the 1990s. Speedometer error—either reading too high or too low—often traces back to a worn or missing driven gear. A damaged gear must be replaced to restore accurate speed indication; no adjustment or repair is possible. The TCI part is a direct replacement that eliminates guesswork during trans rebuild or repair work.