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C6 Transmission Spotlight

C6

The Ford C6 is a heavy-duty automatic transmission built by Ford Motor Company between 1966 and 1996. It was marketed as the “SelectShift Cruise-O-Matic.” Compared to its predecessor MX transmission, the C6 offered lower weight, less complexity, less parasitic power loss, and greater torque capacity for larger engines. It did this without exceeding the packaging dimensions of the MX. These design goals were in line with those of the C4 for smaller engines.

To cut down on weight and cost, the C6 featured a simple, three speed Simpson planetary gearset as well as over 10 lb (4.5 kg) of powdered metal. To increase shift quality and long-term durability, it became the first automatic transmission designed to use the Borg-Warner flexible shift band. The C6 also included disc clutch plates instead of bands on the low and reverse gears, including new composite plates and valves. This gave it the capability to handle upwards of 475 ft-lb of torque.

Prior to 1966, Ford FE and MEL big-blocks were fitted with cast-iron MX and FX 3-speed automatic transmissions. In 1966, Ford introduced its own heavy-duty C6 3-speed automatic transmission for high-torque applications behind large-displacement big-block V-8s. Although the C6 has a completely different case and external components than the C4, it is virtually the same internally to the C4—on a larger scale for heavy-duty use.

The C6 was produced with four basic bell housing bolt patterns over its long production life and is a very rugged transmission designed for high-power applications. The round six-bolt pattern is for FE-series big-block, which includes the 332, 352, 361, 360, 390, 406, 427, and 428 engines. There is another distinctive six-bolt bell housing pattern for the 429/460-ci 385-series big-blocks and the 351M and 400M Cleveland-based, raised-deck V-8s. The six-bolt pattern arrived to the C6 in 1968 with the 429/460 big-block V-8s. There’s also the small-block C6 originally intended for 351W and 351C engines, which fits any six-bolt 289/302/351W/351C small-block bell housing bolt pattern.

By the 1970s, Ford had a respectable lineup of modern lightweight automatic transmissions. An ironic footnote to this story is the weighty cast-iron FMX transmission, which remained in production until 1981 behind 351W small-block engines. It was an easy off-the-shelf solution for Ford, which needed the FMX to keep up with production demands when there weren’t enough C4 and C6 transmissions to go around.

Later, there was a C6 transmission produced for Diesel engines beginning in the 1980s, before the E4OD (4R100) was introduced in 1989. The long history of production really highlights this transmission’s reputation for durability. Despite the E4OD’s presence, Ford still continued to build the C6 up until 1996 for many commercial and industrial applications.

The C6 transmission is still very popular in the sport of drag racing today, with units equipped with manual valve bodies and transmission brakes. It is also widely used in off-road applications due to its reputation of being nearly indestructible. They are available in small block, big block or round bell housing depending on the motor you want to equip it with. We can custom build these to meet or exceed your expectations, check out our store to find out more.