Ford C6 Transmission (Complete Guide)

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You are restoring an old Ford with a Select-shift Cruise-O-Matic transmission, but what should you know about the C6 automatic transmission?

The Ford C6 Transmission (SelectShift Cruise-O-Matic) was a 3-speed automatic transmission with Ford Big-block V8s from 1964 - ‘96. Designed to be a lighter, more durable automatic than its predecessor, the Borg-Warner MX, was built to provide torque and speed control during lower gears.

When it first appeared on the ‘65 Ford Fairlane, Ford knew it could no longer have a cumbersome cast iron transmission to go with the larger block V8s consumers wanted. Desperate to match the growing demand for automatic transmissions and the higher power buyers seem to prefer, the company introduced the new SelectShift Cruise-O-Matic. Built with an aluminum housing, it featured less power loss, more torque, and speed control than the outdated Borg-Warner MX. The C6 transmission is known for its durability and longevity and is a favorite for drag racing applications. It remains a favorite among classic restorers and car enthusiasts even after 60 years due to its ease of upgrading.

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What Prompted Ford To Develop The C6?

With the advent of the muscle car, Ford needed a transmission that could do justice to both the small block and the larger V8 engines it was developing. The previous FX (small block) and MX (big block) Borg-Warner transmissions were complex and cumbersome, with heavy clutches that tended to bog down the transmission. While these transmissions might have done well to power vehicles from the late 50s, Ford saw an opportunity to gain an advantage over GM’s PowerGlide 2-speed.

In addition, the new Ford C6 transmission was much cheaper to produce, which meant their workers could push more of them off the factory line in the time it took to assemble the MX. For Ford, it was a win-win scenario. The new transmission would attract new customers, save money while being produced, and mean more profits.

Ford knew that pairing such a stiff cast-iron transmission like the MX with a larger iron engine block was a recipe for disaster for the hot-rodders, racers, and public wanting faster speeds. The company needed a way to offer better control and break-away speeds at the lower rpm range (for the dragstrip or red light dares) while simultaneously making their vehicles lighter to compensate for the weight of a large V8.

To solve the weight problem and ensure that Ford vehicles crossed the finish lines first, they revamped the transmissions, trading cast iron casings for lightweight aluminum. The C6 has an integrated housing melded with the bell housing as a single unit, which gave it a distinct shape compared to the older, more squatty Borg-Warners used before.

The new transmission added a third low-range gear allowing the driver to choose which gear (first or second) to start rather than revving through a series of gears to reach higher cruising speeds. This unique feature helped on the drag strip and roads that might have been slippery or steep inclines where engine braking might be needed.

Even though there is an additional gear plate, the C6 has a much simpler transmission than its predecessor. Ford took the knowledge they had gained from the introduction of the C4 and adapted the Simpson planetary gear system rather than the twin plate automatics, which were so prevalent. Heat vents were molded into early models to prevent overheating (later models used trans fluid coolers), and new disc-type plates were geared around a central input shaft. The changes meant the transmission could handle vehicles up to 475 ft-lb of torque.

In the early years, the Ford C6 automatic transmission was optional on most vehicles across the lineup. It was a part of some notable brands on the Ford, Mercury, and Lincoln lineups, including the ‘67 - ‘73 Mustang, ‘67 - ‘96 F-Series, ‘67- ‘78 Mercury Cougar, and ‘67 - ‘80 Ford LTD, as well as many others.

What Are The Gear Ratios?

The following table shows the gear ratios for the C6 transmission that Ford produced.

First Gear Second Gear Third Gear Reverse
2.46:1 1.46:1 1.00:1 2.00:1

Where Was the C6 Transmission Made?

The C6 began production in the mid-sixties at Ford’s center of operations for automatic transmissions in Livonia, Michigan (A western suburb of Detroit). In the eighties, the builds were moved to the Sharonville transmission plant in Ohio, where it continued to be made until the C6 was discontinued in 1996.

Ford Motor Company phased out the durable transmission in favor of overdrive drivetrains that were gaining popularity for larger, more extensive V8s. Ford had already switched to the Borg-Warner T18 and 19 to power its truck lineup.

What Are The Specs Of The C6 Transmission?

The following information can help you should you be trying to rebuild a C6 transmission.

Item Spec
Weight 140 lbs
Length 22 3/8s inches
Transmission Fluid 7 quarts - (3 additional for Torque Converter)
Type of Transmission Fluid FA type
Tailshaft 17.1 inches (Lincoln)
14 inches (Ford - Merc Cars)
7 inches (Trucks - SUVs)
Bolt Pattern Various (depending on the engine)
Torque Convertor Various (depending on engine)

The C6 automatic transmission used four different bolt patterns depending on the engine that it got married with. Each of them is a six-bolt pattern, but they are not interchangeable. The round six-bolt pattern for cast iron FE engines is the most prevalent. Those engines include the 332, 352, 361, 360, 390, 406, 427, and 428 engines.

Please note: Since it was adapted to various engines across the Ford, Mercury, and Lincoln lineups, the factory offered different bolt patterns and bell housings. Any restorers should ensure that the specs match before ordering replacements.

How Did the C6 Become the SelectShift?

Until this time, Ford had been using the Borg-Warner transmissions that were outdated, two-speed, that went under different labels depending on the whims of the marketing folks. The existing transmissions were known as Ford-O-Matic, Merc-O-Matic, and Cruise-O-Matic. Since most owners were already familiar with the 2-speed automatics (Ford came out with its first automatic application in 1951), the transition was easy.

SelectShift was added to the name when the new C6 appeared on the scene. The term was coined because the transmission allowed the owner to select which low gear they wanted to have to produce needed extra torque. The P-R-N-D-2-1 pattern helped customers who might need extra traction to get out of the snow or if the engine needed to assist on steep inclines. (Americans were exploring the country like never before, and they welcomed a way not to wear out their brakes when pulling heavy campers behind them).

Eventually, the SelectShift name stuck, and from 1967 on, you find the term plastered across the sales brochures for most Ford models.

Were There Problems With the Ford C6 Transmission?

While the demand for the new SelectShift transmission was so consistent that Ford couldn’t make them fast enough, even though they have an indestructible reputation, some issues emerged, creating trouble for owners.

Some of the problems reported involved no forward or rear shifting ability, slipping in and out of gears (especially on 4x4), and getting stuck in lower gear without moving into the cruising speed of the third gear.