Fiesta ST180 B6 4.3:1 final drive replacementFord Fiesta ST180 EcoBoost 4. 3: 1 Final Drive Increases Acceleration and 0 60 time. Direct Stock OE replacement. Genuine Ford Replacement Parts Parts supplied Crown Wheel Main Output Shaft Pinion 6th Gear Pinion Main Output Shaft Bearing The Original IB6 type Gearbox has a Final drive ratio which is designed primarily for economy not performance. by increasing the ratio from the original 3. 8: 1 to this 4. 3: 1 version you are effectively taking top