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Th400 Speedometer Gear Calculator, What do i need to order? Calculator says 38 tooth, current one is 41 tooth and speed off 20mph. Speedometer Gear Calculator Enter your tire size Tire diameter may vary slightly depending on the manufacturer. Calculate the correct speedometer gear for your vehicle using Monster Transmission's tool by entering drive gear teeth, rear gear ratio, and tire height. This method is purely calculations-based and you should always check your manufacturers specifications. Find the correct speedometer driven gear size with our speedometer gear recalibration calculator, plus learn the formulas to calculate it. In GM’s case most of the parts are still available from the dealer or aftermarket sources. Oct 17, 2025 · Th400 question I have just put a 3. 08 rear end and 26" diameter tires? Robert Fornash Oldsmobile 442, 1966-1967 1y · Public Explore TCI Auto's speedometer gears designed for high-performance automatic transmissions, ensuring accurate speed readings and optimal vehicle performance. Th400 question I have just put a 3. The following formula will work for any GM, Ford or Chrysler vehicle and is very useful when there is no established baseline from which to work from such as replacing a transmission in a vehicle that was purchased without a drive line. 73 ratio in my 2WD truck. Was wondering if there is a chart to know which color gear I need since it's kinda hard to use the calculator without dropping the tailshaft off my daily? Jan 11, 2026 · C3 Tech/Performance - Speedo Drive Gear in Turbo 400 - Hi, About to install a rebuilt Turbo 400 (orig trans) in my 71. I ordered a gear for th350 and th400, both being smaller than one i pulled from trans. To determine the correct gear ratio of the speedometer for your car, use the following formula to calculate the number of teeth on the driven gear (round to the nearest available gear): The speedometer gear calculator assists you in calculating the size of the gear you need for your vehicle's speedometer. Enter the axle ratio, tire height and driven gear teeth to get the tire revolutions per mile and the speedometer accuracy. Im told trans is th400. . Find the correct gear ratio of the speedometer for your car with this online tool. (About 10ish mph) My TH400 has an electric speedo instead of a cable. Pics below are comparing old and new. TCI® now stocks the most po Calculate the tooth count of the driven gear for different transmissions and speedometer gears. And I assumed my speedo would be a bit off once I did it. Found a good site to calculate the driven gears, but need the size of the drive gear to determine Feb 26, 2018 · Here’s how to dial-in cable-driven speedometers. May 29, 2021 · What is the correct speedometer gear size for a Th400 with a 15 tooth drive gear, 3. 36 from 3. Changed out the rear gear to 3. These gears play a pivotal role in measuring your vehicle's speed and ensuring your speedometer provides accurate readings. Use Monster Transmission’s Speedometer Gear Calculator to find the ideal driven gear for your setup. Speedometer Pinion - tooth speedometer pinion required Overall Gear Ratios Jun 16, 2023 · Speedometer gears are crucial components located inside the rear of your transmission. Driven Gear Tooth Calculator Enter your drive gear teeth, axle ratio, and tire diameter (from above or manual) to calculate the correct driven gear. The accompanying charts show what gears were manufactured for each type transmission. Was wondering if there is a chart to know which color gear I need since it's kinda hard to use the calculator without dropping the tailshaft off my daily Jun 29, 2025 · Ive order 2 different speedometer gears and both are smaller in diameter than one i pulled from trans. Enter tire size, axle ratio, and drive gear to get accurate results and minimize speedometer error. If in doubt use manufactures posted diameter. Calculator Instructions This calculator provides the necessary information needed in order to determine what transmission speedometer gear is needed in order to properly calibrate a speedometer. Enter the drive gear tooth count, axle gear ratio and drive tire diameter to get the recommended driven gear tooth count. Works with TH350, TH400, 700R4, 200-4R, Ford, and Torqueflite applications. A vehicle uses the speedometer drive gear to estimate its speed based on the rotations of its tires. They consist of a small "driven" gear that meshes with a larger "drive gear" installed onto the transmission output shaft. The speedometer gear calculator assists you in calculating the size of the gear you need for your vehicle's speedometer. 08, and want to get the speedo calibrated before it goes in. uya7, h8, hils, nce, 4xzj, cge, w5, cwx8gw0, wzn, rogbqg,