C6 automatic transmissions were a product of the Ford Motor Company. The C6 was manufactured between 1966 and 1996 and was equipped with three forward speeds and reverse. The internal planetary gears rotated within a steel drum that was held captive by a fibre-lined band when the vehicle was in motion. As the fibre became worn from use, it would cause a "slip," in the shifting. The band can be adjusted to eliminate the slip with the proper tools and basic automotive know-how.
Park the vehicle on a flat, firm surface. Place the shifter in the "Park" position and set the hand brake. Place wheel chocks around the front and back of the rear wheels.
Raise the vehicle following the manufacturer's instructions as outlined in the owner's manual. Place each jack stand under the steel framework near the front tires. Lower the vehicle slowly until its full weight is on the jack stands.
Locate the C6 band adjustment bolt. The band adjuster is located on the right side of the transmission housing as viewed from the rear. Identify the bolt by its square head, exposed threads and a locknut at its base.
Loosen the locknut by turning it counterclockwise a few turns with an adjustable wrench. It is not necessary to remove the nut.
Turn the square-head bolt clockwise using a 3/8-inch drive inch-pound torque wrench fitted with a 3/8-inch-diameter,12-point socket.
Tighten the band adjustment bolt to 120 inch-pounds using the torque wrench.
Remove the torque wrench and socket.
Turn the band adjustment bolt in a counterclockwise direction one and a half turns with an adjustable wrench.
Hold the band adjustment bolt in place with one adjustable wrench and tighten the locknut with the other adjustable wrench. Turn the locknut clockwise and tighten securely.
Raise the vehicle off the jack stands with the vehicle jack and remove the stands.
Lower the vehicle to the ground and remove the jack and the wheel chocks.
The Ford C6 was replaced by the E4OD transmission. The E4OD was modified to include a fourth forward speed with electronic shift controls.