This new mainshaft internal speedometer gear fits 4 speed toploader transmissions. Typically fitted to Toploaders when when factory fitted with 3.5 or lower gears (higher numerical number) See attached chart to help you decide what you require based on gearing and tyre height 6 Tooth Black OEM number: C5ZZ-17285A

Toploader transmissions were fitted with either of two mainshaft drive gears. 

Black gears were used for rear end gearing from 2.75 to 3.5

Pink gears were fitted for rear end gearing for 3.5 to 4.11

 

Use this handy chart to calculate your requirements

Based on 25.4" Tall Tyre

Driven Gear Pink Gear Black Gear
16 Teeth 3.25 2.75
17 Teeth 3.50 3.00
18 Teeth 3.70 3.25
19 Teeth 3.90 3.36
20 Teeth 4.11 3.55