Speedo Housing GM Trans 7/8 Diameter 18-23T Cnt

The Speedo Housing GM Trans 7/8 Diameter 18-23T Count is a precision speedometer gear housing designed for classic General Motors automatic transmissions. Built to restore accurate speedometer function in TH250, TH350, and Powerglide-equipped vehicles, this component replaces OEM units that have worn, broken, or stripped internal gears. The 7/8-inch (0.875") diameter housing accepts 18- to 23-tooth replacement gears, allowing technicians to calibrate speedometer readings for different final drive ratios and tire sizes.

Speedometer gear housings function as the mechanical interface between the transmission's output shaft and the speedometer cable. Over time, the nylon or plastic teeth on internal drive gears wear or break, causing the speedometer needle to drop, bounce erratically, or stop entirely. The TCI 880021 housing is engineered to accept multiple gear tooth counts within the 18–23T range, making it versatile across different drivetrain configurations. Technicians can select the appropriate tooth count to match the vehicle's axle ratio and tire diameter, ensuring factory-accurate speedometer calibration during transmission rebuild or restoration work.

This housing is essential for restoration shops, transmission rebuilders, and enthusiasts performing complete powertrain overhauls on 1960s–1980s General Motors vehicles. Whether rebuilding a TH250 in a Chevelle, a TH350 in a Camaro, or a Powerglide in a vintage truck, sourcing the correct speedo housing prevents costly post-rebuild complaints about inaccurate speedometer behavior. The compact 3.5 x 1.35 x 6.4-inch form factor integrates seamlessly into factory transmission housings.