by George Reid
Literally millions of Ford cars and trucks were equipped with C4 and C6 automatic transmissions between the introduction of the C4 in 1964 and the replacement of the C6 in the 1980s. These purely mechanical (no electronic controls) automatic transmissions are still popular with racers, hot rodders, and restorers today due to their simplicity and low cost. Cores can be purchased and rebuilt to suit the needs of a specific vehicle for much less than a comparably rebuilt modern overdrive automatic transmission with electronic controls. But, they lack the overdriven gears and lockup torque converters the newer transmissions rely upon to boost fuel economy figures.
Ford had a fundamental challenge to its direction and future in the late 1950s—how to shed a stodgy image and dated technology. This effort began with a new generation of skirted-block FE-series V-8 engines in 1958. In 1960, Ford introduced its lightweight-iron Falcon and Comet sixes. The 90-degree Fairlane small-block V-8s followed in 1962. Prior to 1960, Ford cars and trucks were burdened with outdated, BorgWarner-designed cast-iron MX and FX automatic transmissions known as Ford-O-Matics, Merc-O-Matics, and Cruise-O-Matics. The MX was a large-case automatic and the FX was small. Although these transmissions were rugged and dependable, they were heavy, complex, and not easily adapted to performance applications. This is when Ford engineers developed lightweight aluminum-case automatic transmissions for an exciting lineup of automobiles that arrived in the 1960s.
When Ford Falcon and Mercury Comet were introduced for 1960, they were available with a new lightweight Ford-O-Matic 2-speed transmission. It was designed and manufactured by BorgWarner for new-generation gray-wall-iron straight-6 and small V-8s. What made the little Ford-O-Matic different than its predecessors was its aluminum case and steel hard parts inside and out. In early applications, the Ford-O-Matic transferred heat to the atmosphere via the torque converter and cooling vents in the bellhousing, instead of using fluid as coolant and a transmission cooler in the radiator. Later versions had a transmission fluid cooler in the radiator. The Ford-O-Matic and Merc-O-Matic were available behind the 144-, 170-, and 200-ci straight-6 engines, along with the 221- and 260-ci V-8s, which came later in 1962. The Ford-O-Matic/Merc-O-Matic had a case-fill dipstick tube. Bellhousing and main case were cast as one to reduce weight and reduce the likelihood of leakage. At first glance, the 2-speed automatic looks like a cast aluminum FX or MX case.
Ford took what it learned from the 2-speed BorgWarner automatic and applied it to the C4 3-speed Cruise-O-Matic that arrived for the 1964 model year. The C4 was produced at Ford’s Sharonville, Ohio, transmission plant for its entire production life through 1981 and was the first automatic transmission Ford designed and built. The C4 employed a new state-of-the-art Simpson compound planetary gear set, which became an industry standard in the years to follow. The C4 got its name from the model year that it entered production: “C” for the 1960s decade and “4” for the year, 1964. This naming practice didn’t last long—witness transmissions to follow like the C3 in the 1970s and C5 in the 1980s.
The 3-speed C4 Cruise-O-Matic was introduced just in time for the 1964 model year. The 1964–1966 C4 was known as the Dual-Range Cruise-O-Matic due to its dual-range shift pattern, which included two driving ranges based on shifter position. For 1967, the C4 went to a more conventional P-R-N-D-2-1 pattern and a different valve body. This C4 Dual-Range is an early V-8 unit with a five-bolt bellhousing. The B intermediate servo cover indicates mismatched parts because the B servo is for six-cylinder engines. Expect to see all kinds of mismatched transmissions.
For one model year only—1964—the C4 had a five-bolt bellhousing for V-8s only. In August 1964, the C4 and the V-8s it was mated to were fitted with a larger six-bolt bellhousing to reduce noise, vibration, and harshness.
For 1967, Ford did away with the Green Dot Dual-Range C4. Instead, it used a redesigned valve body offering a P-R-N-D-2-1 shift pattern known as Select-Shift. This valve body was used from 1967 to 1969. A redesigned C4 valve body and transmission case came along in 1970, which was used for the C4’s production life through 1981. In Drive, the C4 shifts the same as the Dual-Range at the large green dot with a normal 1-2-3 upshift program and the same gear ratios throughout. If you want to start out in low gear on snow and ice or to creep along in slow traffic, all you have to do is place the shifter in “2” (second gear) for controlled starts and no upshift.
As the C4 evolved, other design changes were introduced. There were C4 transmissions with pan-fill dipstick tubes (blended case and bellhousing with 164-tooth flexplates). Most C4s were case-fill (notched case and bellhousing with 157-, or 148-tooth flexplates). Pan-fill C4 transmissions with 164-tooth flexplates and blended bellhousings were designed for full-size car and truck applications and are not recommended for compacts and intermediates because they just don’t fit.
The 148-tooth bell and flexplate were designed specifically for Mustang II and Pinto/Bobcat/Capri with small transmission tunnels and are very hard to locate these days. There was also a version of the C4 produced with the 385-series (429/460) big-block bellhousing bolt pattern factory installed behind the 351M and 400M raised-deck Cleveland small-blocks in the 1970s. The 351/400M C4 is extremely rare because so few were produced.
The pan-fill C4 really is more about strength for heavy-duty applications like full-size cars and trucks than anything else because the bellhousing bolts to the case outside the pump housing. Case-fill C4 transmissions are light-duty; the bellhousing bolts to the front pump instead of the main case.
The 1964–1969 C4 input shaft and clutch hub size was .788 inch with a 24-spline on both ends. In 1970, Ford gave the C4 a larger input shaft and clutch hub measuring .839 inch with 26 splines on both ends for improved durability. From 1971 to 1982, the C4 had a split-spline count. It had a .839-inch input shaft with a 26/24-spline configuration, meaning a 26-spline at the torque converter and a 24-spline at the clutch hub.
C4 valve body variations are important to note because they’re significant to your transmission-building project. At this time, I’m aware of at least four different types of C4 valve bodies and I suspect there are more out there. For 1964–1966, there’s the Dual-Range/Green Dot valve body. At a glance, the Dual-Range valve body looks identical to 1967–1969. Internally, it has different valving and shift programming.
There’s also the 1967–1969 valve body, which offers a conventional P-R-N-D-2-1 shift pattern.
For 1971–1981, the C4 valve body changed significantly and does not interchange with 1964–1969 bodies due to changes in the case. Case and valve-body bolt patterns changed for 1970–1981, which is why a 1964–1969 valve body does not fit a 1970–1981 case.
C4 Gear Ratios
First Gear 2.46:1
Second Gear 1.46:1
Third Gear 1.00:1
Reverse Gear 2.20:1
In 1982 Ford introduced the C5 Select-Shift transmission, which was nothing more than a C4 with a locking torque converter to improve fuel economy. The C5 was in production between 1982 and 1986 at the Livonia, Michigan, transmission and axle plant and is not recommended as a performance transmission as received from the factory. However, C5 cases and many internal components are similar or identical to the C4, and are quite suitable for performance applications thanks to their improvements, as discussed in Chapter 4.
Like the C4, C5s were produced as both case-fill and pan-fill with either 157- or 164-tooth flexplates. None were 148-tooth flexplate. What makes the C5’s main case desirable is improved oil circuits and some improvements to case strength.
Prior to 1966, Ford FE and MEL big-blocks were fitted with cast-iron MX and FX 3-speed automatic transmissions. For 1966, Ford introduced its own heavy-duty C6 3-speed automatic transmission for high-torque applications behind large-displacement big-block V-8s. Alth-ough the C6 has a completely different case and internal components than the C4, it is virtually the same internally to the C4—on a larger scale for heavy-duty use.
The round bell, six-bolt C6 transmission for FE-series big-block V-8s. A C6 is easily identified by its one-piece bellhousing and main case design.
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 bellhousing bolt pattern.
Finally, there was a C6 for Diesel engines beginning in the 1980s, before the E4OD (4R100) was introduced in 1989, punctuating this transmission’s reputation for durability. Despite the E4OD’s presence, Ford continued to build the C6 until 1996 for industrial applications.
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.
Here’s the C6 for 385-series 429/460 big-blocks as well as the 351M and 400M raised-deck small-block Cleveland V-8s, quickly identified by its finned case.
This B&M small-block C6 looks a lot like the big-block C6 unit except it’s a small-block six-bolt bellhousing design. This case is also ribbed for strength.
C6 Gear Ratios