Ford C4 Transmission Speedometer Gear Calculator, Free USA Shipping. . This 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! This will calculate the speedometer driven gear needed to properly calibrate your speedometer. These gears do not fit the 4 speed Toploaders as they have reversed tooth direction. Always recheck the speedometer calibration! You can either enter your radial tire dimensions or actual measured values below. May 8, 2020 ยท Get the right speedometer gear for your 1979-98 Mustang based off of rear gear ratio & tire size! No guessing with this Mustang Speedometer Gear Calculator! This C4 and FMX Automatic Transmission Overhaul Manual is a brilliant resource for restoring, maintaining or repairing your Ford engine. Available in 16, 17, 18, 19, 20, 21 or 23 Tooth Gear. 1967 - 1973 Mercury Cougar (and Ford Mustang) Speedometer Gear Calculator Use this TCI Auto Speedometer Gear Calculator Formula for any GM, Ford or Chrysler vehicle. Please see worldwide shipping calculator in this list ing. This method is purely calculations-based and you should always check your manufacturers specifications. 7bv, 7rms, iutxqr, tleairbl, q36, 3wc, p4yr, ie, dt4dv, an,