Speedo Gear Driven GM 43t Purple

The Speedo Gear Driven GM 43t Purple is a precision speedometer drive gear engineered for General Motors automatic transmissions, including the TH200C, TH375B, TH425, TH475, and 700R4 models. This component is essential for vehicles requiring speedometer calibration adjustments—whether you're running non-original tire sizes, installing a higher-ratio differential, or swapping transmissions between platforms. Mechanics and enthusiasts rely on gear-driven speedometer systems because they provide reliable, mechanical accuracy without electronic drift, making them ideal for restorations, performance builds, and daily drivers alike.

Manufactured from durable plastic composite, the 43-tooth driven gear meshes directly with the transmission's speedometer drive gear to transmit rotational speed data to the instrument cluster. The purple color coding helps technicians quickly identify tooth count during installation and verification. Unlike electronic speedometer corrections that require reprogramming, this mechanical gear solution offers instant accuracy without additional modules or wiring modifications. The compact design—measuring just 2.85 x 2.1 x 4.1 inches and weighing only 0.14 lbs—fits seamlessly into the transmission housing without requiring case modifications or custom fabrication.

Installation is straightforward for experienced mechanics: remove the speedometer cable or electronic sensor, extract the old driven gear, and replace it with the 43-tooth variant. Gear selection depends on your tire diameter and axle ratio—the 43-tooth specification works well for moderately lifted trucks or vehicles with larger tires that would otherwise show lower speeds than actual. This product is compatible only with GM transmissions featuring gear-driven speedometer systems, making it unsuitable for vehicles with electronic speed sensors or non-GM platforms. Verify your transmission model and current gear ratio before ordering to ensure proper calibration.