What's the Ford axle code c8?

The Ford axle code C8 means that the gear ratio in the differential is 2.73. This means that the wheels spin one time every time the drive shaft rotates 2.7 times. If You need to replace the gears due to damage or when You want to upgrade the ratio You will have to drain the differential first. Crawl underneath the rear of the vehicle and place a drain pan below differential and remove the drain plug. You can now remove the fill plug above the drain plug. Keep in mind that the differential fluid is quite thick and will take a while to fully drain out. Once the fluid flow is down to just a drip You can go ahead and remove the bolts from the backside of the differential and take off the cover.