RTS OE Speedometer Gear, 23 Tooth, For Ford Automatic C4 C5 C6 FMX AOD, Will Fit T5 Tremec TKO Magnum, Driven Gear, 3.9, EachThis new speedometer driven gear fits C4 C5 C6 C10 FMX AOD transmissions. Tip: If you can determine whether your speedometer is reading too slow or too fast, it is worth noting that a lower # of teeth will cause it to turn faster versus a higher # of teeth to turn slower Speedo Gear Suit 3. 7 4. 11 C4 C5 C6 C10 FMX Approx 25 27 Inch Tyre Size This is a retro fit gear to allow the speedometer to function with 3. 73 and 4. 10 rear end gears. Since the