Ford’s C4 Cruise-O-Matic and Select-Shift 3-speed automatic transmission is a light-duty unit intended for six-cylinder and small-block V-8 engines. Versions of the C4 have also been produced for big-blocks. The C4 was produced from 1964 through 1981 at Ford’s Sharonville, Ohio, transmission plant. An interesting footnote is the C4’s status as the first automatic transmission ever designed and actually produced by Ford Motor Company. It is one of the easiest automatic transmissions to rebuild and modify because it is so simple and there are a lot of seasoned racers and builders who know a lot about this transmission and how to get it to perform.
Like GM’s Powerglide and Turbo- Hydramatic 350, and Chrysler’s 904 Torqueflite, Ford’s C4 is a simple light-duty transmission you can knock down and rebuild in your home workshop. There are different approaches as to how to build a C4 and what to put in it. Seems everyone has a different opinion about how to build one for street and competition.
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The C4 is an extremely rugged 3-speed automatic transmission capable of withstanding tremendous amounts of power. Even with the best factory parts, the C4 is a hardy box that will serve you for years and thousands of miles with regular fluid and filter changes. As a drag racing automatic, there are a lot of drag-tested components out there designed to enable a C4 to withstand 600 to 1,000 hp on the quarter-mile, making the C4 competitive with GM’s legendary 2-speed Powerglide. Savvy transmission guys in the industry have told me they’ve seen a C4 take as much as 1,200 hp, though I wouldn’t suggest pushing a C4 that far. Anything beyond 600 hp presents risk, but that’s racing. Street and weekend-racing C4s can easily handle 250 to 600 hp without breaking a sweat.
During the C4’s long production life, it underwent several changes you should know about before getting started. From 1964 to 1969, the C4 had a .788-inch, input shaft 24/24-spline, which can take up to 400 hp. In 1970, Ford went to a larger .839-inch, 26/26 spline—one year only. It’s very hard to find a 26/26-spline shaft if you’re building a 1970 core and need an input shaft. The following year, 1971, Ford changed the input shaft again to a split 26/24-spline type, which means the torque converter end gets a 26-spline and the forward clutch hub gets a 24-spline.
The 26/26 and 26/24 shafts take up to 600 hp, though you should go with a hardened, aftermarket 26/26-spline shaft from TCI Automotive or Performance Automatic if you’re going to push it beyond 450 hp. Performance Automatic’s hardened input shafts, as one example, are forged from 4340 steel and are engineered for up to 185,000-psi tensile strength, which matters greatly if you’re going racing.
Knowing what you have is important when you’re looking for C4 cores and parts. Ideally, you can find a complete 1971-or-newer C4 transmission core that already has these changes because very little changed through the end of C4 production in 1981. This means there is an abundance of C4 cores available from 10 years of production so you can build the kind of transmission you need for street or strip.
There were two C4 shift patterns employed during its production life. From 1964 to 1966 came the Green Dot Dual-Range shift pattern transmission. In normal driving, the shifter should be positioned on the large green dot at the detent where the transmission does a routine 1-2-3 upshift. If you want to start out in second gear with the Dual-Range C4, you place the shifter at the small dot (off detent, next to neutral) where the transmission starts out in second gear and upshifts into final drive. The small-dot position was a feature designed to help motorists get started on snow and ice. You don’t want the Green Dot valve body for a good street/strip C4 unless you’re concerned about originality in a 1964–1966 Ford or Mercury restoration.
Beginning in 1967, Ford went to a more conventional P-R-ND- 2-1 shift pattern for the C4. It was known as Select-Shift, which meant a redesigned valve body that was used through 1969. This is the valve body you want for your 1964– 1966 C4 street/strip transmission because it drops right in without modifications. You have to change your shifter to a P-R-N-D-2-1 with the change to a 1967–1969 valve body. If you start out in second gear with this 1967-on pattern, there is no upshift out of second, which makes the 1967-on Select-Shift shift function differently than the earlier 1964–1966 Green Dot, which does upshift.
For 1970-on, there was yet another revised valve body (eightbolt versus nine-bolt) along with a corresponding change in the transmission case. This means the ninebolt 1970-on valve body works with the 1964–1969 eight-bolt C4 case with the added bolt and a locknut. However, the eight-bolt valve body does not work with the nine-bolt 1970-on case. My best advice is to go with a 1970-on transmission case and valve body rather than try to mix the two.
C4 transmissions were originally fitted with factory identification tags located at the intermediate servo cover. Because so many of these tags have been discarded by transmission builders through the years, identification often has to be determined in other ways. And in some instances, it really doesn’t matter because castings and parts speak for themselves with numbers of their own. What matters most is the case, bellhousing, tailshaft, tailshaft housing, and key internal parts like the forward clutch and input shaft. It must all work together smoothly and reliably, which depends on you using compatible parts. Identification can be determined through Ford casting numbers, date codes, and visual identification of these components.
Case-Fill or Pan-Fill
Although there were a variety of C4 castings produced between 1964 and 1981, there are but two basic types you can expect to find: stepped and blended-bell cases with a wide variety of tailshaft housings and bellhousings. The stepped bell, also known as case-fill, has a sevenbolt (bellhousing-to-case) bellhousing that bolts to the front pump and is designed for compact and intermediate applications, though it can be installed in full-size cars and trucks. The case-fill has a dipstick tube provision in the left-hand side of the case, hence the term case-fill.
The blended-bell case is known as a pan-fill because the dipstick tube goes into the pan instead of the case. This type is for heavy-duty applications in full-size cars and trucks. The pan fill/blended bellhousing bolts to the main case instead of the front pump and has a larger five-bolt bellto- case pattern for less noise, vibration, and harshness, along with better load distribution.
The pan-fill C4 does not fit compact and intermediate Fords and Mercurys due to dipstick tube clearance issues with headers and frame rails. If you find a pan-fill C4 for your Mustang, Fairlane, Torino, Falcon, or Comet, it won’t fit. Instead, find a stepped bell/case-fill core because fitment is nearly impossible and always frustrating with the pan-fill C4. Seasoned transmission builders view the pan-fill C4 as the strongest case available. However, fitment is tricky to impossible in compacts and intermediates, which leaves you with case-fill only.
Another main case option available to you is the 1982–1986 C5, which is compatible with the C4 in terms of key components that interchange. The C5 case has better hydraulic/lubrication circuits along with larger cooler-line fittings. When I ask transmission builders what they think of C4 versus C5 main cases, most take the C5 over the C4 when possible due to improved hydraulic circuitry and cooling. However, most also say there’s little difference between the two unless you’re building an all-out drag racing transmission.
The C5 was produced in both stepped-bell and blended-bell configurations as well as 157- and 164- tooth flexplates. You may even use the stepped-case C5 with a 148-tooth flexplate for Mustang II and Pinto.
Another item to watch for is five- versus six-bolt bellhousing-toengine- block bolt patterns with C4 transmissions. Although finding an early-1964-only, five-bolt C4 bellhousing is a long shot these days, they’re out there and are quite valuable because so few remain. The problem is, a fivebolt bell does not fit a six-bolt block. Unless you have a 1962–1964 221-, 260-, or 289-ci engine with a five-bolt block, you need the improved six-bolt C4 bellhousing.
Another bellhousing fact that can catch you off guard is the wider C5 bellhousing used only on the 1982–1986 C5. Because the C5 has a locking-clutch torque converter for improved efficiency, the converter is wider and, therefore, needs a wider six-bolt bellhousing. If you use the C5 bellhousing on your C4 and try to fit it into a classic Mustang, you’re in for a rude awakening because it does not clear the tunnel. It does not match up with your flexplate, front pump, or starter either. Look for E2, E3, E4, E5, and E6 casting numbers on this bellhousing. It is just as easy to use a C4 bellhousing on a C5 case because you’re not going to be using a locking torque converter with C4 components.
Another important consideration is the size of flexplate and bellhousing you intend to use. The C4 was manufactured with a variety of bellhousing and flexplate configurations—157- and 164-tooth are the most common. You probably see more 157-tooths than anything because the C4 was installed in more compacts and intermediates than any other Ford transmission.
The 164-tooth flexplate and bellhousing were more common to fullsize cars and trucks, though they were fitted to 289 High Performance V-8 applications in compacts and intermediates. The main consideration is to make sure you have a bellhousing and flexplate that match. Where building a C4 becomes tricky is for the 1974–1978 Mustang II, 1971–1980 Pinto or Bobcat, and any Mercury Capri before 1979. Because the transmission tunnels on these particular vehicles were small, Ford developed a smaller 148-tooth bellhousing/flexplate combination. Most of you know Pinto, Bobcat, and Capri were never factory fitted with a V-8. However, a few of us like V-8s in these classic subcompact Fords and Mercs. Whatever subcompact platform you choose for your project, you’re going to need the smaller 148- tooth bellhousing and flexplate.
Where it becomes frustrating is trying finding a 148-tooth bellhousing/ flexplate comboanywhere. There may be a few laying around, but most are gone, victims of clunker laws and crusher programs. Salvage yards remain among the few sources for these rare pieces. If all else fails, one of the best sources is Transtar for new parts. For used parts like bellhousings, there are Ford specialty parts dealers around the country all too happy to help you.
In order to best understand how to build a C4, you must first know how it operates. The C4 transmission employs a conventional fluid coupling known as a torque converter. The torque converter connects the engine’s crankshaft with the transmission’s input shaft via a fluid coupling, and it multiplies the engine’s torque under acceleration with a process as time-proven as a goodold- fashioned water wheel. With the shifter in neutral, the torque converter, input shaft, and forward clutch whirl around at the engine’s speed. Hydraulic fluid under pressure continues to circulate through the front pump, the torque converter, and return to the sump. Unless you place the shifter in one of three ranges, this is how the transmission operates with the engine running.
When you place the C4’s selector in Drive, fluid under pressure is routed to the forward clutch beginning at the manual shift valve. From the manual shift valve on, it gets complicated.
Engine power travels through the forward clutch to the forward ring gear hub and ring gear. When power is applied, it flows to the forward ring gear, which drives the front planet carrier, which is splined to the output shaft. The front planet pinions then rotate clockwise and the sun gear rotates counterclockwise. As the sun gear rotates counterclockwise, you get clockwise rotation of the reverse planet carrier.
Because the reverse planet is held stationary by the one-way roller clutch and reverse band, the output shaft ring gear then rotates around the reverse planet pinions. Output shaft ring gear rotation is then transferred to the output shaft ring gear hub.
This rotation then causes the forward planet to rotate clockwise, only slower than the ring gear for a 2.46:1 ratio (2.46 revolutions to 1 revolution of the output shaft). If the selector is placed in Low, the low-reverse band is applied, which then makes engine braking under deceleration possible.
When there’s sufficient speed, the C4 upshifts into second gear. Second gear also happens when you manually place the selector in second or Drive 2 (DR2). When this happens, there’s forward clutch engagement (already happening in first gear) and intermediate band application (second gear only).
With this turn of events, power flows through the forward clutch to the front planetary-ring gear hub, which is tied to the output shaft. Power stops at the front-unit ring gear. The ring gear then rotates around the front planet gears, which are tied to the front planet carrier, which is tied to the output shaft. Front planet gears rotate around the stationary sun gear, which is connected to the input shell. The sun gear is held still by the intermediate band, which is locked around the reverse-high clutch drum. The reverse-high clutch drum is connected to the input shell.
At this point, power is flowing through the front planet carrier to the output shaft for a gear reduction of 1.46:1 (1.46 turns of the input shaft for every 1 rotation of the output shaft).
When it is time for upshift into direct or final drive, both the forward clutch and reverse-high (direct) clutch are applied. As both clutches are applied, the entire geartrain is turning in the same direction at the same speed meaning input and output shafts are turning at the same speed in the same direction. There is no gear activity in direct or final drive for a 1.00:1 ratio. One full rotation of the input shaft equals one full rotation of the output shaft.
In reverse gear, you apply the reverse-high clutch pack and lowreverse band. Power flows to the input shaft through the forward clutch to reverse-high clutches and drum to the input shell, which is tied to the sun gear. The sun gear is driven by the input shell, which drives the reverse planet gears. The reverse planet pinion gears drive the reverse ring gear in the opposite direction.
In other words, the input shaft turns one way and the output shaft is driven in the opposite direction.
The low-reverse drum is locked by the low-reverse band, which keeps the rear planet carrier from turning.
Power flows through the reverse planet pinions to the ring gear, which drives the output shaft. This gives you a 2.20:1 ratio (2.20 turns of the input shaft for every 1 rotation of the output shaft).
Building a Better C4
Because you want the most reliable performance possible from your C4 build, you’ll want to choose the best components available. Leon’s Transmission has chosen B&M Racing & Performance for this C4 build. And because there’s no real magic going on here, knowing what to use is a matter of doing what the experts who build high-performance C4 transmissions do. Because most of you reading this book are building street and weekend race transmissions, you’re going to want reliable feedback.
Experts and racers generally believe the blended pan-fill C4 case is the strongest C4 case; however, it faces space limitations with subcompact, compact, and intermediate Fords. This means you are limited to the stepped-bell, case-fill C4 for your less-than-large Ford. The news isn’t all bad however.
If originality and matching numbers aren’t important to you, go with a 1971-on C4 core with a 26/24-spline input shaft and forward clutch, which is the easiest C4 generation to build in terms of parts and availability. You may also go with the 1982–1986 C5 stepped-bell, casefill main case and C4 bellhousing to achieve the most reliable C4 possible. All you have to do is fill it with C4 internals and make the necessary modifications, which are minimal.
When it comes to case-fill versus pan-fill, the C4’s dimensions speak for themselves. The blended bell, pan-fill C4 does not fit your compact or intermediate without serious compromise. But with the right combination of parts, a stepped-bell, case-fill C4 offers convenience and is capable of staying together at more than 600 hp.
After you’ve selected the right C4 main case and bellhousing for your project, turn to what goes inside. Unless you are committing your C4 transmission to full-time drag racing, you’re not going to need a manual valve body or a trans brake. The main focus of this book is street and occasional drag racing.
If you have a 250- to 350-hp small-block or a six, a stock C4 with the standard complement of V-8 clutches (sixes have fewer) and a shift improvement kit delivers the kind of performance you need for the street. Reliability comes from a firm shift instead of a soft shift, where slippage and friction burning occur. You don’t want a harsh shift unless you’re going racing. The key to reliability is the type and number of clutch frictions and steel thicknesses you’re going to use, along with setting proper clearances.
The C4 has been factory fitted with a variety of intermediateband servos for an even wider range of applications. The most popular intermediate-band servos are the C, H, and R, which have the largest piston and bore size for maximum band pressure. The most common is the A servo found on most small-block C4s. Six-cylinder units have the B servo, which isn’t recommended.
Though racers and builders have a real obsession with the C, H, and R servos, in truth there’s not much difference in performance from one servo size to the next. Transmission professionals I’ve worked with have proven the H and R servos provide the best intermediate-band apply pressure, which is based on having the largest cover and piston size. An added twist to servo selection is how quickly the servo releases the intermediate band during 2-3 upshifts. You want the quickest release possible at wide-open throttle without RPM flare. This is why the R servo is more favorable than the H, if you can find one.
You want the most piston/bore surface area possible for maximum hold. However, what also matters a lot with the intermediate band is how wide the friction area is coupled with the type of friction material. Drag racers prefer Kevlar and Blue intermediate bands because they hold and release better, and last much longer in tough racing competition. Kevlar makes very little sense for the street considering the cost involved and minimal benefit gained.
Because the low-reverse band doesn’t get the kind of workout the intermediate band does, I’m not concerned with making changes here because it has absolutely no real effect on performance.
In all the transmission builds I’ve seen through the years, I’ve never witnessed modifications to the front pump. They just seem to keep going and going. The main concern is cavity and gear condition, along with proper operation of the pressurerelief and drain-back valves.
Check fluid passages for debris. Always replace the bushing and seal. The front pump is just that— a positive-displacement hydraulic pump that provides control pressure and lubrication. This means it doesn’t require much attention aside from inspection of gears, cavity, and valves, plus replacement of bushing and seal. Unless a pump ingests foreign matter or becomes cavitated during operation, there’s little chance of damage or extreme wear.
C4 valve bodies boil down to four basic types: 1964–1966 Dual-Range, 1967–1969 nine-bolt, 1970-on eightbolt, and 1971–1980 Pinto/Bobcat (also eight-bolt). There are other minor differences too numerous to mention. What you’re concerned with most is basic valve body types.
Trans-Go, B&M, and TCI Automotive offer shift improvement kits for the C4 that not only firm up shifts, they also add longevity because they reduce and eliminate clutch and band slippage. They enable the valve body to apply more pressure to band servos and clutches. It is also the timing of clutch and band application and release that makes these kits so effective.
Throttle Valve Operation
Working with the valve body is the C4’s throttle valve, also known as the vacuum modulator. Your C4’s throttle valve senses engine load and the need for torque by getting its signal from intake manifold vacuum, which acts on the throttle valve’s diaphragm, spring, and rod. When vacuum drops (open or wide-open throttle), the throttle valve increases control pressure through the valve body and contributes to the delay of upshift at wide-open throttle. When intake manifold vacuum is high (closed throttle), the throttle valve helps the valve body lower control pressure and prompt a more immediate upshift.
From a performance standpoint, there’s not much you need to do to the throttle valve, aside from choosing one you can adjust and tweaking its adjustment to suit proper transmission function. Remember, the throttle valve is important to transmission control pressure, which means being careful with how you make adjustments. Poor vacuum valve adjustment can lead to transmission failure because control pressure is critical here. Hindrances to control pressure can cause slippage, heat, and wear. This is why this valve is so important to proper function.
To adjust the throttle valve properly, you’ve have to know the control pressure, which involves a pressur gauge at the control pressure port just above the manual shift and neutral safety switch. Transmission sump temperature should be at hot idle. Cold transmission fluid gives you an erroneous pressure reading on the high side because the fluid is more dense. The gauge’s pressure range needs to be 0 to 400 psi.
First, you must establish proper throttle valve function. Does the throttle valve work properly? Is there vacuum leakage? This is checked with the throttle valve removed using a vacuum pump or an intake manifold vacuum from an operating engine at idle. At 18 to 22 inches of vacuum, you are able to tell if there’s leakage by a hissing sound or the absence of diaphragm/rod movement. There should also be diaphragm and rod movement at 18 to 22 inches of vacuum. At higher elevations, your engine may struggle to maintain 18 inches at idle.
With the throttle valve installed, transmission in neutral/park, and engine at idle, you should have a minimum of 18 inches of manifold vacuum. Anything lower than 18 inches of vacuum indicates engine health problems that must be corrected or you have a really lumpy camshaft profile. If you have at least 18 inches of vacuum and the selector is in any forward gear, you should see 55 to 62 pounds of line pressure (55 to 100 pounds in reverse).
With the throttle open at 10 inches of vacuum and the transmission in any forward gear, you should see 96 to 105 pounds of line pressure. At 3 inches of vacuum, expect to see 138 to 148 pounds of line pressure in any forward gear. In reverse at 3 inches, expect to see 215 to 217 pounds of line pressure.
Whenever line pressure isn’t within these parameters, throttle valve adjustment must be done with great care. When line pressure is too high, shifts become harsh. If line pressure is too low, shifts become soft (slippage) and that’s when there is damage with burned clutches and bands. To increase control pressure, throttle valve adjustment needs to be clockwise. To reduce line pressure, counterclockwise. Ford says one full turn either way adjusts line pressure 2 to 3 psi. Check line pressure at idle, then, at 10 and 3 inches of manifold vacuum to determine if any further adjustment needs to be made.
Never base your adjustments on shift feel alone because that isn’t wholly what line pressure is about. Always use a pressure gauge and follow Ford’s guidelines to the letter.
Building the C4
Although automatic transmissions can be very intimidating, they really are engineering marvels that have only gotten better with time and improved engineering. And though they’ve become more complex, their basic concept hasn’t changed much in a half century. The C4 remains one of the simplest automatic transmissions ever produced, which means you can build this transmission with confidence if you follow instructions and take your time.
Because manufacturers, such as B&M Racing & Performance, have developed kits and parts for Ford automatic transmissions, it has become easier to source what you need to perform a rebuild in your home workshop. And, if B&M doesn’t have it, Transtars are available at a host of local transmission parts suppliers from coast to coast.
When sourcing parts for your C4 build, never cut corners in your efforts to save a few bucks because it isn’t worth sacrificing durability. You get what you pay for. Do it on the cheap, and you have to go back inside sooner. In few places is this more true than clutches and bands.
You want the best friction materials possible. This doesn’t mean going with racing clutches and bands in your C4 because, although they work quite well short-term, they don’t last long-term. The best street frictions are those red factory original pieces.
Kevlar bands work quite well for allout drag racing but make no sense on the street. And their cost doesn’t justify their use on the street either.
Your C4’s greatest asset isn’t always the parts, but the assembly technique practiced during build-up. It is those details missed that come back to haunt later. Again, remember what you observed during the disassembly. The cause of transmission failure can be an important detail missed during assembly. Prior to assembly, closely re-inspect all parts for unusual wear patterns or damage.
One thing you want to be prepared for is small changes that happened in C4 production, such as low-reverse clutch-return spring design. Early in production, Ford used 10 low-reverse clutch return springs. Later, in the 1970s, Ford went to one large return spring to reduce costs and improve clutch performance.
The reverse-high clutch assembly does not have to involve special tools. You may use four C clamps to compress the spring and install the C-clip. When you do this, take care to protect your eyes and face.
During geartrain assembly, it is easy to get lost in the details. Thrust washers, which take up endplay and give components thrust support, are easy to overlook. Instead of thrust washers, late-model automatic transmissions like the AOD, AODE, and 4R70W have Torrington (roller) bearings, which reduce power-robbing internal friction throughout the geartrain.
If you want to reduce internal friction your C4 can be fitted with Torrington bearings. However, Torrington bearings, and modifications designed to accommodate them, do not come cheap. But if you’re going racing, they make your C4 more efficient and add power.
More for Your C4
Although this book is slanted toward the street and occasional strip enthusiast, it’s always nice to know there’s help if you want a little something more from your C4 build. Because the C4 is an extremely rugged box that takes a lot of punishment, you can run a lot of power through it, even using factory pieces such as clutches and bands.
The best pieces are factory C4 components that came along after 1970. And you just can’t beat what the aftermarket has come up with since 1970. Ford’s C4 enjoys the same notoriety with racers as GM’s legendary Powerglide, thanks to its lightweight, back-yard simple design. And there are plenty of them out there.
Step-1: Begin Assembly
Assembly on this 1974 Ford C4 Select-Shift transmission begins with the front pump assembly. Install bearing race and front seal first, with generous lubrication on both. Be sure you have inspected drive and driven gears along with the case, checking for abnormal wear patterns. It’s easy to get gear installation backward, where torque converter flats won’t engage driven gear flats. Make sure driven gear flats are open to the torque-converter side. Otherwise, you won’t be able to seat the torque converter, which drives the pump. Pack pump cavities with transmission assembly lube for generous lubrication on startup.
Step-2: Inspect Sealing Rings (Critical Inspection)
Pump stator support sealing rings and contact surfaces should be closely examined for wear, scoring, and proper fit. This means both stator support and forward clutch contact surfaces. Some builders use Teflon sealing rings with great success. But Teflon is more appropriate for racing applications, though there are bound to be arguments on this one. Much depends on how you intend to use your C4 transmission. Teflon seals are easier than iron rings on the hard parts, but iron rings tend to last longer because there’s not as much difference in hardness.
Clutch Pack Assembly
Step-1: Begin Forward Clutch Assembly
Forward clutch assembly begins with piston seals, which go on the clutch cylinder and clutch piston. Seals get generous amounts of transmission assembly lube. Make sure seals are seated squarely in grooves. A twisted or disfigured seal fails, so make sure seals are seated square as clutch piston is installed.
Step-2: Lubricate Forward Clutch Cylinder
Generously lubricate the forward clutch cylinder with transmission assembly lube to ensure smooth operation on start-up. Dry seals are damaged on start-up. You can never have too much lubrication.
Step-3: Secure Clutch Piston
After forward clutch piston is installed, this snap-ring is next to secure clutch piston.
Step-4: Inspect Belleville Spring (Critical Inspection)
This is the Belleville spring, also called a disc spring, which returns the forward clutch piston to rest, releasing clutches when hydraulic pressure is released. This is a good time to inspect the Belleville spring for cracks. Small hairline cracks can cost you time later.
Step-5: Remove Forward Clutch Segments
Forward clutch segments are next, beginning with this steel. There are four or five clutch frictions in a stock C4 V-8 forward clutch. Sixes have four, as a rule. You really want five clutches.
Step-6: Clean Clutch Frictions
Always soak new clutch frictions in transmission fluid before installation. There’s no real harm in installing dry clutches, but it makes more sense to get started with saturated frictions.
Step-7: Install Forward Clutch Frictions
Forward clutch frictions and steels installed. Steels are driven by the clutch cylinder (also called a clutch drum). Frictions (clutch plates) drive the ring gears and planetaries. Clutch clearances should be .022 to .042 inch, determined primarily by snap-ring thickness. Selective snap-ring thicknesses are .088, .092, .074 to .078, or .060 to .064 inch. This may vary considerably in the aftermarket. Steel thicknesses also vary, which affects clearances. Be prepared to measure them with a micrometer and then check clearances with a thickness gauge after installation.
Step-8: Install Reverse-High Clutch Piston
Be sure to install a reverse-high clutch piston with new seals and plenty of lubrication. You want things real slippery for a good healthy start-up. Reverse-high clutch return springs do differ in old-versus-newer C4 units. Early units have 10 small clutch-piston return springs, which is what you witnessed during disassembly. This mid-1970s C4 unit has a single large return spring. Be prepared for engineering changes like this in your C4.
Step-9: Install Reverse-High Snap Ring (Special Tool)
Use a spring compressor to install a reverse-high clutch-piston snap-ring. You can do this in your home garage with four C-clamps. And this is the only phase of C4 assembly where any kind of special tool or fixture is required.
Step-10: Assemble Reverse-High Clutch
Reverse-high clutch (also called a direct clutch) assembly begins with the first steel for a total of four clutches. Some applications have three frictions. But it is possible to get five clutches in a stock drum/cylinder depending upon both the clutch drum and clutch steel thicknesses. Aftermarket direct clutch drums take as many as seven clutches for improved power transfer without power loss due to slippage. The more friction surface you have going here, the better.
Step-11: Check for Proper Function
Air-check the forward clutch for proper function. Air moves the forward clutch piston, which can be heard and observed as air is applied. Do this with the forward clutch mated to the front pump/stator support assembly.
Step-12: Install Thrust Washer
Prior to installing the ring gear/hub, install the number-3 thrust washer. Use plenty of transmission assembly lube on contact surfaces.
Step-13: Reassemble Planetary/Clutch
Forward planet carrier and ring gear/hub go together along with the number-4 thrust washer on the backside of the carrier.
Step-14: Connect Forward Clutch and Ring Gear
Mate together the forward clutch and ring gear, which takes practice. Spline the forward clutch hub and ring gear into clutch frictions by gently working the ring gear back and forth until fully seated. Note that in this photo the forward planet carrier is not installed in the ring gear. This ring gear drives the forward planet.
Step-15: Connect Planet Carrier to Ring Gear
The forward planet carrier is meshed into the ring gear, which is seated into the forward clutch. (Note: the reverse planet carrier and reverse-high clutch cylinder are already assembled).
Step-16: Examine Subassembly
Take a close look at this subassembly to verify the order of components from top to bottom—forward planet carrier, forward clutch ring gear/hub, forward clutch, and reversehigh clutch.
Step-17: Install Shell & Sun Gear
Input shell and sun gear go on top, mated to the forward planet and reverse planet carrier.
Step-18: Dress Case Mating Surfaces
Dress the transmission case mating surfaces with a stone to achieve a perfect surface to prevent leakage. As surfaces are stoned, irregularities appear.
Step-19: Replace Low-Reverse Servo Piston
The low-reverse servo piston should always be replaced. Check for proper fit, then lube for installation. Install it smoothly until seal is submerged. Be careless here and you not only damage the seal, but also will have to replace the piston.
Step-20: Replace Low-Reverse Servo Cover Seal
Low-reverse servo cover gets a new seal, which should be lubed with transmission assembly lube. Slowly run the bolts down until the cover is fully seated, and then torque to 12 to 20 ft-lbs in crisscross fashion.
Step-21: Replace Intermediate-Band Servo Piston Seal
Intermediate-band servo piston gets new seals and plenty of transmission lube to ensure proper sealing and operation. Lube the seals prior to installation for best results. Best servos are H or R types for full-size Fords and trucks, which are the largest and provide the greatest apply area for better band hook up. They also offer the quickest release time, which is important to crisp performance. The C servo you often hear about is for the 289 High Performance and is harder to find. The C servo is also available as a reproduction from Scott Drake Reproductions if you’re determined to have one.
Step-22: Prepare Intermediate Servo Cover and Piston (Professional Mechanic Tip)
Steve Bunch of Leon’s Transmissions suggests using a super-thin film of non-hardening Permatex Form- A-Gasket for optimum sealing of the intermediate servo cover, though most transmission techs never use sealer. The problem with C4s is leakage, which calls for extreme measures. In some instances, it is acceptable to use sealer, but only a non-hardening type and sparingly. If it comes out around the edges, you’re using too much.
Gently press the intermediate-band servo piston into the servo cover. Be very careful about seal lubrication and protection. It is easy to unknowingly damage seals and then be faced with leakage when the unit is in the car. Save time by slowing down and getting this right.
Step-23: Apply Assembly Lube
Install servo cover, piston, and spring with transmission assembly lube. Torque cover bolt to 12 to 20 ft-lbs in a gentle crisscross motion until tight. Do not overtighten.
Step-1: Begin Main Case Assembly
With all subassemblies complete, you’re ready to assemble the main case, which begins with the number-9 thrust washer at the roller clutch. You can see that the roller clutch outer race has already been installed. Lubricate the thrust washer with transmission assembly lube.
Step-2: Install Roller Clutch Spring Retainer
Roller clutch spring retainer (also called a cage) is next. Some incorrectly call this a sprag clutch.
Step-3: Inspect Inner Race
The roller clutch’s inner race ultimately splines inside the low-reverse drum once the roller clutch is assembled. It is shown here with the low-reverse drum and hub. The roller clutch (not pictured) allows low-reverse drum rotation one way, but not the other
Step-4: Install Inner Race (Documentation Required)
The inner race fits in the center of the roller clutch. Note how the spring retainer, roller, and spring go together—with only one set installed here. There are 12 rollers and 12 springs. Install the springs as shown here. It is easy to get the springs backward, which results in prompt transmission failure. Spring lip must point toward the outside of the case at the roller and toward the inside opposite the roller. Rollers lock against the rise in the case, which is how this works as a one-way clutch. Like a ratchet in your toolbox, the one-way clutch allows rotation only one way.
Step-5: Install Parking Pawl
The installed parking pawl, return spring, and gear.
Step-6: Install Governor Distributor
Governor distributor is installed next, gently tapping it into place. There are no gaskets or seals here, just a snug interference fit.
Step-7: Inspect for Wear (Critical Inspection)
Replace all iron sealing rings. Inspect the governor distributor contact surfaces inside for wear prior to tailshaft installation.
Step-8: Install Tailshaft
Use transmission assembly lube to lubricate tailshaft seals. Install the shaft, gently working them into the governor distributor. A key to reliable assembly is being gentle. Force stubborn pieces together and you damage critical surfaces and parts.
Step-9: Install Low-Reverse Band
First install the low-reverse band, the large band, which has been soaked in transmission fluid. Follow transmission case provisions for clearance and the low-reverse band goes right in. Expect some stubborn interference issues here. Be patient and it drops right into place.
Low-reverse band and drum look like this when properly installed. On the right is the parking-pawl mechanism rod and detent spring.
Step-10: Install Number-6 Thrust Washer
Reverse planet carrier receives the number-6 thrust washer, which is lubricated with transmission assembly lube. Tabs seat into provisions in the reverse planet carrier.
Step-11: Install Number-7 Thrust Washer
Number-7 thrust washer goes on this side of the reverse planet carrier. Have you inspected reverse planet carrier pinions for excessive wear and oscillation? Now is the time to be absolutely sure about wear.
Step-12: Install Reverse Ring Gear & Hub
Number-8 thrust washer is already installed at the low-reverse drum inside the case. Tailshaft retention C-clip is already installed. Now install the reverse ring gear and hub.
Step-13: Install Reverse Planet Carrier
Fit the reverse planet carrier into the reverse ring gear already installed in the case. Reverse planet drives the reverse ring gear and tailshaft. Tailshaft is splined into the reverse ring gear hub.
Step-14: Install Input Shell/Forward Clutch
Forward clutch, reverse-high clutch, and input shell are already assembled and ready to be fitted into the reverse planet carrier. The input shell’s sun gear fits into the reverse planet carrier. You have to rock this assembly back and forth to achieve proper planet carrier mating.
Step-15: Install Intermediate Band
Fit the intermediate band around the reverse-high clutch drum. Although this intermediate band is dry, soak it prior to installing it. With street/strip applications, this is the friction material you want (in red); it offers longevity. Blue and Kevlar racing frictions offer outstanding hookup, but a short lifespan.
Step-16: Install Front Pump
With a long punch carefully guide the front pump into place; to where the stator support slides into the forward clutch. Did you remember to install the gasket? Some C4 and C5 applications have an O-ring instead of a gasket. Make sure the O-ring is thoroughly lubricated.
Step-17: Torque Bolts (Torque Fasteners)
Use a high-temperature thread locker on pump bolt threads for added security. Torque bolts to 28 to 40 ft-lbs in crisscross pattern for even torque.
Step-1: Install Governor Screen
Install the governor filter (screen). It keeps stray particles from adversly affecting governor operation. Do not forget this piece, even if your C4 didn’t have one to begin with. You can get one from Transtar or just about any local transmission-parts supply house.
Step-2: Install Governor
The governor installs on the tailshaft. Note primary (right) and secondary (left) valves. Primary valve goes to work at 10 mph to get things started. Secondary valve determines shift points based on vehicle speed.
Install the governor and torque bolts to 80 to 120 in-lbs. Note that is inch-pounds, not foot pounds. Applying too much torque distorts the governor, rendering it useless.
Step-3: Apply Yoke Seal
Apply a thin film of Permatex Form-Agasket non-hardening yoke seal to the tailshaft. This is old technology, but still a very effective sealer.
Step-4: Install Intermediate Band Adjustment Screw
Install the intermediate band adjustment screw along with the locknut. C4 band adjustments are all coarsethread. C5 intermediate band adjustment is fine-thread, while low-reverse is coarse-thread.
Step-5: Install Struts & Intermediate Band
Here you get a look at the low-reverse band, struts, servo rod, and adjustment screw. Install the intermediate band between the low-reverse band and the servo rod.
Step-6: Adjust the Bands (Professional Mechanic Tip)
Tighten in this sequence: intermediate band to 10 ft-lbs torque and then back off 1½ turns. Low-reverse band to10 ft-lbs and then back off 3 full turns. Locknuts to 35 to 45 ft-lbs. Not every transmission shop adjusts bands this way. Many have developed their own technique through the years, based on what works well for them, but this is what Ford suggests. Make sure adjustment screws do not turn when you’re tightening locknuts. Locknuts have integral seal lips to keep fluid inside.
Step-1: Replace Shaft Seal (Professional Mechanic Tip)
Manual-shift shaft passage gets a new seal. Make sure this seal gets generous lubrication with either transmission fluid or assembly lube before shaft installation. Shaft nut is tightened with a 7/8-inch open-end wrench.
Step-2: Install Valve Body
Manual-shift valve (bottom) is tied to manual-shift control linkage. Kickdown valve (top) is depressed by the kickdown linkage at wide-open throttle.
When installing the valve body, carefully guide manual shift and kickdown linkages into proper positions. Visually ascertain proper location and function of each before closing up.
Step-3: Install Transmission Pan
Apply a very thin film of Permatex Form-A-Gasket (non-hardening) between the case and the gasket and allow to set before you install the pan. This is one key to a leak-free installation. You want a pan that’s distortion free, which means no irregularities. (New stamped-steel pans are available from Scott Drake Reproductions dealers.) If you want fluid to run cooler, go with a cast finned aluminum pan. The downside: cast aluminum pans tend to bleed fluid through casting irregularities. Although I’ve seen GE Glyptol used on the inside of cast aluminum pans, some brands of transmission fluid can break down the Glyptol.
Step-4: Install Converter (Important!)
Install the converter (here a B&M Holeshot with 2,400-rpm stall speed) and take extra care to properly seat input shaft and pump flats. Proper fitment boils down to feel—first the input shaft, and then the pump flats. If you can fit your fingers between converter and front pump, the converter isn’t seated properly. Before installing the converter, pour at least 1 quart of transmission fluid into the converter to help prime the system for generous lubrication and pressure on start-up.
Written by George Reid and Republished with Permission of CarTech Inc