You can calculate the needed speedo gear teeth with the formula below.
speedo gear Teeth=Drive Gear Teeth (Times) Axle Ratio (Times) Tire Rev. Per Mile Divided By 1000
The drive gear teeth number on a 65/66 C4 is 7, if the cougar you took the trans out of had tall gears it might have a 6 spline tailshaft (6 drive gear teeth).
-JON
|