Ford’s C6 transmission was first pressed into service for 1966. It was designed to replace a generation of heavy and outdated BorgWarner MX and FX iron-case transmissions used behind Ford big-block and Y-Block V-8s. The C6 is on a par with GM’s Turbo- Hydramatic 400 and Chrysler’s 727 Torqueflite transmissions. It is a heavyduty 3-speed automatic transmission designed primarily for high-power V-8 engines and employs a conventional, non-locking torque converter.
Internal C6 architecture isn’t much different than that of the smaller C4 introduced in 1964 (see Chapters 4 and 5). The C6 differs in its size and having a larger case—where bellhousing and main case are one integral casting. This means you are faced with choosing between at least four basic types of C6 bellhousing patterns. Here’s what you can expect to find and how to differentiate between them:
This Tech Tip is From the Full Book, HOW TO REBUILD & MODIFY FORD C4 & C6 AUTOMATIC TRANSMISSIONS. For a comprehensive guide on this entire subject you can visit this link:
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385-Series 429/460 and 351/400M
6.9L/7.3L Diesel Engines
Angular six-bolt (with closed bottom)
Six-bolt similar to 385-Series (with open bottom)
The C6 consists of a torque converter, front hydraulic pump, Simpson compound planetary gearsets controlled by one band, three disc clutches, a single one-way roller clutch, and a simple mechanically controlled hydraulic control system.
The C6 differs from the smaller C4 in its low-reverse function. Instead of a low-reverse drum as in the C4, you instead have a low-reverse clutch package tied to the case, which performs the same function in a C6. This means the C6 is equipped with one band and servo instead of two.
For its first year, 1966, the C6 was a Dual-Range Cruise-O-Matic Green Dot transmission like the C4, where normal driving takes place on the green dot at the detent. For special driving conditions on snow and ice, the small dot (off detent) starts you out in second gear, with upshift into final drive once you get going. For the first-year the C6 was a standalone unit, meaning the valve body was Dual-Range for that year only.
For 1967, the C6 became Select- Shift with a routine P-R-N-D-2-1 shift pattern just like the C4. For slippery conditions, you start out in “2” or second gear to get going. To get an upshift into final drive, you must move the shifter into “D” or Drive.
Aside from minor changes in the 1970s and 1980s, the C6 didn’t change much over its long production life from 1966 to 1996. The C6 remained in production long after it was dropped from Ford passenger cars and trucks because it remained popular with companies that needed it for heavy-equipment applications.
C6 function isn’t much different than you find in the C4 with the exception of having a low-reverse clutch instead of a low-reverse band and clutch drum. Function begins with the front pump, a simple gear pump that provides hydraulic pressure for operation and lubrication for moving parts. The system is protected with drain-back and pressure-relief valves. The drain-back valve keeps the torque converter full after shutdown. A pressure-relief valve prevents overpressure and catastrophic failure.
The C6’s power flow follows the same path as the C4’s except for the low-reverse function. You get better load distribution and torque multiplication through Simpson planetaries and a ring gear around a sun gear. And this is where you are in first and second gear.
The objective is to get power from the input shaft to the output shaft via a series of planetaries and clutches. The C6’s input shaft is splined into the forward clutch. In neutral, the forward clutch turns with the input shaft and torque converter turbine. With all of its clutches and steels, the forward clutch transfers power to the ring gear, which is mated to the forward planet carrier.
The forward planet carrier is tied to the output shaft via the sun gear. When the transmission is in first or second gear, the forward planet is always in motion.
Through the Gears
As the reverse-high clutch (direct clutch) and input shell come into play, power begins to flow. The reverse-high clutch rides on the pump stator. It is also mated to the forward clutch. When you apply the reversehigh clutch, it engages the forward clutch. The reverse-high clutch is linked to the input shell, which is connected to the sun gear. As power flows to the sun gear, it travels to the low-reverse or rear planet carrier to the low-reverse ring gear, which is splined to the output shaft.
For the most part, I’ve described C4 function to this point with the same cast of players. The C6 differs in where the power travels at this point. Instead of a low-reverse band and clutch drum, you have a low-reverse clutch locked into the transmission case. When you apply the intermediate servo and band to the forward clutch cylinder, power is channeled through the forward planet, which becomes second gear during the 1-2 upshift.
In first gear, the input shaft turns the forward planet, which reverses input shaft rotation to the sun gear. The sun gear is splined into the lowreverse (rear) planet, which again reverses rotation to the output shaft. This gives you a gear reduction of 2.46:1 (2.46 revolutions to every 1 revolution of the output shaft).
In second gear, fluid under pressure energizes the intermediate servo, thereby locking the band, forward clutch drum, and sun gear. The forward planet rotates around the sun gear, which provides support at this point. This drives the forward ring gear, which drives the output shaft in the same direction at a ratio of 1.46:1.
When a C6 shifts into final drive, the intermediate band releases the forward clutch drum, and both forward and reverse-high (direct) clutches are applied. With the reversehigh and forward clutches applied, both input and output shafts are connected and the entire package rotates at the same speed for a 1.00:1 ratio.
In reverse gear, the low-reverse clutch is applied to hold the reverse planet stationary. When this happens, the reverse-high clutch is applied to get the input shaft tied to the sun gear. Because the reverse planet is held still, this causes the sun gear to be driven in the opposite direction as the input shaft. This turns the the ring gear, which is tied to the output shaft, at a ratio of 2.175:1.
Pressure Relief Valves
Hydraulic pressure is there for control and lubrication purposes in the C6. Pump pressure, also known as line or control pressure, has to be controlled for proper and safe operation. Fluid flow begins at the pump cavity and flows into the torque converter. This is why it is important to have fluid in the converter during installation. Fluid in the converter primes the system and gets fluid moving from the sump to the pump to the converter. It’s a momentum thing.
There are two valves important to this discussion: the drain-back valve and the converter pressure-relief valve. The drain-back valve’s job is to keep fluid in the torque converter after shutdown. It unseats at 5 psi during engine start and allows fluid flow. The converter pressure-relief valve, which vents to the sump during overpressure (90 psi), is next in line. The main regulator valve is next, which regulates control pressure.
Next in line is the governor, which is mounted on the tailshaft. The governor has two valves that work hand in hand. The primary valve starts to work when vehicle speed reaches 10 mph. This keeps the governor from going to work below this speed. Once the primary governor opens, allowing fluid pressure to pass, the secondary valve comes on line as a means of controlling the shift point based on vehicle speed.
Valve piston movement is countered by spring pressure. As vehicle speed increases, centrifugal force causes the valve pistons to override spring pressure and the valves open one at a time with corresponding speed.
Throttle Valve Operation
Shift control is determined by both the vacuum modulator (throttle valve) and the kickdown linkage after the governor comes on line. Kickdown linkage is for wide-openthrottle operation. As with the C4, the C6’s vacuum modulator ties manifold vacuum to transmission control pressure. The greater the intake manifold vacuum, the lower the control pressure for a sooner, softer upshift. When we have low intake-manifold vacuum at wideopen throttle, the throttle valve helps increase control pressure for a firm upshift, which is what you want at wide-open throttle.
As with the C4, throttle valve adjustment on the C6 is key to proper operation and reliability. You’ve got to get this right or face slippage and transmission failure. To adjust the throttle valve properly, you’ve got to know control pressure, which involves a pressure gauge at the control pressure port just above the manual shift and neutral safety switch. Transmission sump temperature should be at a hot idle. Cold transmission fluid gives you an erroneous pressure reading on the high side because the fluid is denser when cold. The gauge 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 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 40 to 61 pounds of line pressure. In reverse, you want 60 to 93 pounds of line pressure.
With the throttle open at 10 inches of vacuum and the transmission in any forward gear, you should see 100 to 114 pounds of line pressure. At low vacuum, expect to see 154 to 180 pounds of line pressure in any forward gear. In reverse at low vacuum, expect to see 234 to 275 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 you do damage with burned clutches and bands. To increase control pressure, throttle valve adjustment needs to be turned clockwise. To reduce line pressure—adjustment is counterclockwise.
Ford says one full turn either way adjusts line pressure 2 to 3 psi. Check line pressure at idle, at 10 inches, and then at 3 inches of manifold vacuum to determine if any further adjustment needs to be made. Never base your adjustments on shift-feel alone; that isn’t what line pressure is all about. Always use a pressure gauge and follow Ford’s guidelines to the letter.
Intermediate Servo and Apply Levers
Servo selection for the C6 isn’t nearly as involved as it is for the C4 because there really is only one type, the R servo, to ensure good intermediate band hook-up and release. But you must be careful to properly match servo covers, pistons, and apply levers. This requires thorough examination of the Ford Master Parts Catalog if you want to be absolutely certain of the intermediate servo pieces you need for your C6.
Expect to find N, L, P, and S servo covers, which are the most common servo covers, though I am sure there are more. The transmission professionals I’ve consulted with all agree on the R servo or an equivalent aftermarket billet replacement. Where it can get tricky is the variety of intermediate servo apply levers.
If you’re going for street/strip performance, you should investigate the 6061-T6 billet-aluminum intermediate servo apply levers available from Sonnax Performance, which offer durability as well as mechanical advantage. Three ratios are available: 1.85:1 (E-ratio), 2.30:1 (F-ratio), and 2.82:1 (FF-ratio).
That way, you know exactly what you have when it’s time to build. And the R servo works well with any of the stock apply levers I’ve seen in a variety of builds. In other words, the R servo is a no-brainer because racers have been using it for decades with great success. The R servo arrived for the C6 with the 428 Cobra Jet engine in 1968 and is a proven performer.
The C6, unlike the C4, uses an intermediate servo apply lever to help provide mechanical advantage to apply the intermediate band. There are six servo-apply-lever ratios to be aware of, and you must be very careful of which ones you use with corresponding servo covers and pistons. Broader Performance advises against the use of the F 2.30:1-ratio apply lever and R servo because shifts become too aggressive and can damage your C6.
Here are the six known Ford servo-apply-lever ratios. The higher the servo-apply-lever ratio, the greater the apply force. These letter codes can be found cast into each apply lever.
Protocol for the C6 front pump is the same as it is for the C4, with no special modifications needing to be made. Inspect the pump cavity and gears for abnormal wear patterns and scoring. Any excessive wear patterns call for pump replacement. TCI Automotive has provided Tom’s Transmissions with a remanufactured front pump assembly ready for installation, although I suggest you never install a component right out of the box without close inspection. And then fill the pump cavity with assembly lube for a good start-up.
Aside from that first year with the Green Dot Dual-Range C6 pattern, the C6 valve body didn’t change much over its 30-year production life. The first-year Green Dot valve body is discouraged unless you’re restoring a stocker and originality is important to you. During the 1970s, the manual valve went from an internal detent to an external detent with a case-mounted detent roller and band. This is something to be mindful of as you amass parts for your C6. Make sure your valve body and transmission case match. If you have the external detent mounted on the case, you want a free-sliding manual valve. If there’s no external detent, you want the valve body with an internal detent with a ratcheting manual valve.
Whenever you source a C6 valve body, always determine origin because applications vary greatly. For example, you wouldn’t want a C6 valve body for a Diesel application for your 390 or 428 because shift programming and overall operation is quite different due to different pressures and calibrations. Diesels call for an extremely firm shift program for a more solid transfer of torque.
Broader Performance offers a reasonably priced variety of C6 valve body packages depending on how you intend to use your C6. Broader Performance goes to extreme detail with its blueprinted valve bodies, offering you everything from a stock auto-shift valve body, manual and reverse-pattern, to pro tree. These valve bodies are machined to provide a perfect mating surface. Then, they’re ultrasonic cleaned before assembly to ensure all debris is removed. Each C6 valve body is assembled and calibrated to your application.
The main thing to remember when searching for a valve body core is to know where it came from for reasons of compatibility and calibration. Read casting numbers and date codes, then, check the Ford Master Parts Catalog to determine origin.
When Ford designed the C6 to begin with, it didn’t mess around. This transmission was designed and produced to be Ford-tough like no other automatic had been to date. This means the C6 takes a pounding with stock components and red street frictions and comes back for more. That’s the good news, and there isn’t much bad. This is an extremely rugged transmission as it came from Ford. For your street build, few modifications are necessary to achieve durability and performance.
The only really bad news with C6 transmissions is internal drag due to dated thrust washer design, which promotes friction. There’s also the excessive weight of those tough internals. Figure on losing 50 to 60 hp just trying to turn a stock C6 transmission, which is why the C4 became such a popular dragracing transmission. But you didn’t read this chapter to learn the C6’s disadvantages—you want to know how to build one. All racers have their C6 tricks, and I touch on a few of them here. The objective is to build a sturdy street/strip/tow transmission that serves you well for thousands of miles.
The C6 was replaced in Ford vehicles by the E4OD 4-speed automatic overdrive transmission in 1989, which has internals very similar to the C6 and an added overdrive unit. In fact, the E4OD utilizes extreme-duty pieces that work well in your C6 build once you know what you’re doing.
Torrington Bearings Instead of using thrust washers, these components are designed to reduce internal friction by using Torrington bearings, which are actually upgrades found in the Ford E4OD heavy-duty overdrive transmission. The E4OD transmission isn’t much more than a C6 with overdrive, a fresh case, and low-friction components inside. The Low-Drag Planetary gear set offers the durability and mechanical advantage of six-pinion performance instead of three each as you find in the C6. Brian Fotrune of Tom’s Transmission is going to build a vintage C6 transmission designed for old-fashioned big-block power yet with engineering refinements that have come since the mid 1970s, including a 2.72:1 first and a 1.54:1 second gear. Although this gearing is engineered for the Modular V-8 and V-10 engines with their different torque curves, it works quite well in drag racing because vintage big-blocks offer you the acceleration advantage.
One of the most important elements of a transmission build is proper seal use and installation. Take note of what type of seal is on each component during disassembly to ensure the same type of seal goes back on. You may find transmission failure from time to time where seals were improperly installed or wrong seals were used. When you install clutch pistons, do it gently and carefully to prevent seal damage, which is one of the leading causes of transmission failure.
Because Brian is going with the TCI Low Gear, Low-Drag package here, there are significant changes happening to the geartrain you need to be aware of. The forward clutch hub, borrowed from the E4OD parts bin, is different than the C6’s and arrives as a part of the TCI kit. Torrington bearings throughout greatly reduce frictional issues.
The TCI Auto six-pinion forward and rear planetary carriers provide greater load distribution qualities than you find on the older C6 threepinion units, which makes our C6 better for durability in racing or towing.
Some transmission techs endorse removal of the wavy washer in the forward clutch for the addition of a clutch friction. We have five clutch frictions as it is, which is satisfactory, and plenty for the street.
And while I am on the subject of clutches, some transmission shops dress the steels for improved traction. However, I’ve never seen steels come out of a box dressed, but instead as raw steel. Clutch drums should be dressed with 400- to 600-grit paper because traction here is critical to better upshifts. The wider you can spec your band width, the better. I cannot overstress the importance of checking clutch clearances followed by an air-check on each.
During forward clutch assembly, pay close attention to the Belleville spring condition. Unseen hairline cracks can cause the Belleville spring to break during that first road test. I am often inclined to suggest a new Belleville spring with every transmission build because this piece gets stressed to where cyclic fatigue takes its toll.
Another issue to watch for is any clutch piston/drum irregularities or scoring. It’s the minute things you cannot see (ragged edges and nicks) at first glance that can cause transmission failure; seals get damaged by these irregularities during installation or start-up.
Building the C6
As shown here, Brian from Tom’s Transmissions builds a street/strip C6 transmission and shows you how to improve both durability and performance with components from TCI Automotive. Here’s what’s on the bench at Tom’s Transmissions from TCI Automotive:
- 1966–1976 C6 Master Racing Overhaul Kit
- 1966–1976 C6 Low Gear, Low- Drag Planetary Set
- C6 Direct High-Performance Friction Clutch Steels (.075 inch)
- C6 Reverse High-Performance Friction Clutch Steels (.075 inch)
- C6 Powerband High-Performance Flex Band
Step-1: Replace Shifter Seals (Important!)
After you replace the manual and kickdown shifter seals this is the end result. Because the C6 has a history of popping into reverse gear without advanced notice, you want to double-check the detent and make sure it is solid and secure. This is a critical safety item; so pay very close attention to detail here.
Step-2: Lubricate Seals
C6 build-up is in subassemblies beginning with the forward clutch shown here. Lubricate clutch-piston seals with assembly lube and roll them into place. Outer seal goes on the piston and inner seal goes inside the clutch drum.
Forward Clutch Assembly
Step-1: Press In Forward Clutch Piston
Gently press into place the forward clutch piston, paying very close attention to seal activity (left). Use great care, walking each seal carefully into place using a seal manipulation tool (right). It is very easy to damage the seals.
Step-2: Install Lock Ring
This lock ring secures forward clutch piston.
Step-3: Insert Belleville spring
Forward clutch gets the Belleville clutch-piston return spring, also known as a disc spring. This spring returns the piston to rest when hydraulic pressure stops.
Step-4: Install Pressure Plate
Forward clutch’s forward pressure plate is next.
Step-5: Install Wavy Washer
After the pressure plate, install this wavy washer. Some transmission professionals suggest deleting the wavy washer and adding a friction. Not everyone agrees on this one. Because there are already five clutch frictions here, this modification isn’t necessary.
Step-6: Insert Frictions and Steels
Alternate clutches and steels with this clutch friction being first after the wavy washer. This particular forward clutch gets five frictions and four steels. The close-up on the right shows how clutch frictions are internally driven. Clearances are determined by snap-ring thickness. There are three selective snap-ring thicknesses for setting forward clutch clearances: .065 to .069, .074 to .078, and .083 to .087 inch.
Step-7: Install Pressure Plate
After you install all clutches and steels, install the pressure plate.
Step-8: Inspect Forward Clutch
Completed forward clutch looks like this at rest with no pressure applied (left). With pressure applied, forward clutch looks like this (right) with clutches compressed and Belleville spring distorted. Note: number-3 and -4 thrusts have both been lubed and installed mid-clutch.
Reverse-High Clutch Assembly
Step-1: Install Reverse-High Piston Seal
Reverse-high (direct) clutch piston receives its seal and generous amounts of lubrication. There’s also an inner seal, which is installed inside the reverse-high clutch drum. Although transmission assembly lube is used here, you can also use Vaseline for seal lubrication.
Step-2: Install Reverse-High Clutch Piston
Gently press the reversehigh clutch piston into place making sure there’s no seal distortion or damage.
Step-3: Install Return Springs and Retainer
Return springs and retainer are next. You can use a clutch spring compressor (shown) or C-clamps for spring compression and snap-ring installation. The number of springs depends on application.
Step-4: Inspect Measure Reverse-High Clutch Pressure Plate (Critical Inspection)
Inspect the reverse-high clutch pressure plate for heat checking and thickness. Thickness determines clutch clearances though adjustment is determined by selective snap-ring thickness.
Step-5: Install Clutches & Steels
Install reverse-high clutches and steels next. This one gets five clutches.
Step-6: Install Pressure Plate
Pressure plate is installed next, after clutches and steels. This is the number-2 thrust washer. Recommended clutch clearances are .022 to .036 inch. Selective snap-ring thicknesses to adjust clearance are .065 to .069, .074 to .078, and .083 to .087 inch.
Step-7: Install Forward Clutch Hub
With TCI’s C6 Low Gear Planetary set, some changes have to be made to accommodate the swap. On the left is a C6 forward clutch hub. On the right, a E4OD forward clutch hub, which enables us to use TCI’s Low Gear Planetary gear set. Move thrust washer over the E4OD hub. This is one of few spots that doesn’t have a Torrington bearing.
Step-8: Insert Retaining Ring
Forward clutch gets a retaining ring for a secure union with the reverse-high (direct) clutch drum.
Step-9: Mate Clutch Packs
Forward clutch is mated to the reverse-high clutch drum. This involves working the forward clutch back and forth until it completely seats in the reverse-high clutch drum. Both assemblies should be completely flush if properly seated.
Step-10: Install Thrust Washers
Numbers-3 and -4 thrusts are installed. This is a low-friction Torrington bearing.
Step-11: Install Hub
Carefully spline the forward clutch hub into the forward clutch. Pay close attention to how the hub feels and confirm it has seated.
Planetary Gearset Installation
Step-1: Planetary Upgrade Option
Now to the real meat of this C6 build— TCI’s Low Gear, Low-Drag Planetary set for 1966–1976 C6 transmissions. On the right is a C6 three-pinion forward planet carrier. On the left is TCI’s six-pinion forward planet, which offers durability plus 2.72:1 first gear and 1.54:1 second gear for crisp acceleration. Low-friction Torrington bearings reduce internal friction by a wide margin.
Step-2: Insert Thrust Bearing
Ready the TCI Low Gear forward planet for installation with this number-5 Torrington thrust bearing.
Step-3: Install Forward Planet
TCI Low Gear forward planet slips right into the forward clutch hub ring gear.
Step-4: Insert Bearing
TCI forward planetary gets this Torrington thrust bearing.
Step-5: Install Shell & Sun Gear
Input shell and sun gear are next, splined into the forward planet. This subassembly is also unique to the TCI Low Gear Planetary gearset for the C6.
Step-6: Inspect Rear Planet
TCI’s Low Gear package (left) also includes a six-pinion rear planet for durability and improved gear ratio. On the right is a factory three-pinion example.
Low-Reverse Clutch Assembly
Step-1: Install Roller Clutch
Low-reverse clutch hub gets its new TCI one-way roller clutch.
Step-2: Install Clutch Piston Seals
Lubricate inner and outer seals before they’re installed. Be careful with some applications, which have a lip seal that must be installed with the lip toward the pressure source. Install a lip seal backward, and you do not contain the pressure. Your first clue is soft or no engagement. Keep in mind what direction the pressure is coming from.
Step-3: Install Clutch Piston
Carefully press the low-reverse clutch piston into the case, watching out for seal distortion. When secure, there are 24 clutch-piston return springs to install.
Step-4: Insert Spring Retainer
Secure the low-reverse clutch-piston spring retainer with a spring compressor and snap-ring. This gets very tricky if you don’t have a spring compressor. You have to rent or borrow one.
Step-5: Install Inner Race
Next install the one-way roller clutch inner race. Make sure to lubricate all surfaces.
Step-6: Install Hub
Install the low-reverse clutch hub, making sure roller clutch fits neatly and smoothly around the inner race. There should only be one-way rotation.
Step-7: Inspect Steels (Critical Inspection)
Inspect low-reverse clutch steels for heat checking.
Step-8: Prepare To Install
Lay out low-reverse clutches, steels, and pressure plate across a workbench in the order of installation.
Step-9: Install Steel
Low-reverse steel goes in first.
Step-10: Install Friction, Steels, Clutches
Low-reverse clutch friction is next, followed by steels and clutches. These clutch frictions are splined into the low-reverse clutch hub.
Step-11: Install Pressure Plate
Low-reverse clutch pressure plate goes in last, including the selective snapring, which is sized to set clutch clearances based on thickness.
Step-1: Inspect Governor Assembly
Disassemble and inspect the governor assembly. You want freedom of piston (valve) movement and proper spring pressures. Check for rattle. All passages should be clear.
Step-2: Reassemble Governor Assembly
After you reassemble the governor assembly it is ready for installation. There is no gasket or seal, only perfectly machined surfaces. Carefully torque governor fasteners to 80 to 120 in-lbs. Never go on feel because overtightening means distortion and valve malfunction.
Step-3: Inspect Rings
Check governor distributor sealing rings for fit and contact surfaces for scoring. Any scoring is unacceptable and must be machined out or replaced.
Step-4: Install Governor
First lubricate the governor distributor sealing rings then slide the assembly onto the output shaft. Remember, there’s a ball that works as a Woodruff key to the spline output shaft and governor. If you forget this ball, your C6’s governor will not work.
Step-5: Inspect Pawl
Inspect and assemble the parking pawl. This weak spot for C6 transmissions must be closely inspected. Check for solid, secure operation because this is a safety item.
Step-6: Install Washer
Lube and install the number-10 thrust washer.
Step-7: Install Parking Gear
Closely inspect parking gear teeth for any damage or potential failure points. Install the gear in the governor distributor sleeve.
Step-8: Install Distributor Sleeve
Press the governor distributor sleeve into place. Torque the bolts 12 to 20 ft-lbs.
Step-9: Install Output Shaft
Lubricate and install the output shaft, making sure it is firmly seated in the case. If the output shaft is hard to turn, check sealing rings, contact surfaces, and governor sleeve for any irregularities. Never force the shaft. Install the C-clip and slide it up to the roller clutch’s inner race.
Step-10: Install Bearing
This Torrington thrust bearing is next.
Step-11: Inspect Installation
The installed low-reverse clutch package should look like this. The low-reverse clutch and hub, one-way roller clutch, and the output shaft are visible.
Step-12: Install Ring & Hub
The reverse ring and hub slide into the low-reverse clutch hub. Make sure all surfaces are lubed.
Step-13: Install Rear Planet
TCI six-pinion rear planet is next and should spline right into the reverse ring gear.
Step-14: Insert Torrington Thrust
Number-7 Torrington thrust bearing is next. Torrington bearings reduce internal friction and free up power.
Step-1: Install Forward Geartrain
The forward geartrain splines right in like this. Input shell and sun gear spline into rear planet.
Step-2: Install Intermediate Band
TCI Powerband intermediate band goes in next. This takes careful navigating to where the band-to-strut contact points fall in line with the adjustor and servo.
Step-3: Align Intermediate Band
Intermediate band and both struts are in place. On the left is the servo apply lever and strut. On the right is the adjuster and strut. Make sure struts are firmly seated (refer to step 13 on page 110).
Step-4: Install Intermediate Servo Apply Lever
C6 transmissions are fitted with a number of different intermediate- band servo apply levers. Each is identified by a letter code and fulcrum design. The base Ford part number is 7330. The A lever (left) has a 1.65:1 ratio. The K (right) is 1.575:1.
Step-5: Inspect Input Shaft
Input shaft should be inspected for abnormal wear and twist. This one has corrosion and should be replaced, though it wouldn’t be an issue in a non-performance application. TCI has a 31/30 spline hardened input shaft for C6 transmissions made from billet steel, a natural complement to the Low Gear system already installed.
Step-6: Insert Splines
Input shaft splines into the forward clutch.
Step-7: Use Grease For Pump Gasket Retention
Apply a thin film of transmission lube for gasket retention prior to front pump installation.
Step-8: Install Front Pump Gears
As long as there’s no damage or excessive wear to the pump cavity, all you have to sweat is bushing and seal replacement. Inspect pump gears and cavity to be satisfied with their condition. Install the gears and fill the cavity with transmission fluid for a good wet start.
Step-1: Assemble Pump
Pull together the pump halves and torque the bolts to 28 to 40 ft-lbs.
Step-2: Install Rings
Front pump sealing rings are gapless. Hook the ends and overlap them to be flush.
Step-3: Install Pump O-Ring
Lubricate and install the pumphousing O-ring seal, making sure seal is square with groove.
Step-4: Install Thrust Washer
This is the number-1 selective thrust washer, located at the front pump, which controls geartrain endplay. If endplay requires adjustment, there are a variety of thicknesses available (.008 to .044 inch).
Step-5: Air-Check Clutch
Reverse-high (direct) clutch can be air-checked through the front pump.
Step-6: Install Pump Gasket
Position the front pump gasket and check for proper alignment.
Step-7: Install Pump Assembly
Line up and install the front pump assembly. Use a center punch for alignment. Install the bolts and use them to run the pump down. Torque is 28-40 ft-lbs. Monitor seal status as the pump seats.
Step-8: Choose Intermediate Servo
This 2.465-inch-diameter servo from TCI (left) offers 25- to 35-percent more apply area than the Ford R servo. This means more apply power for your C6’s intermediate band. This billet aluminum intermediate assembly (PN 423005) is a big step up from the Ford R servo (right), which is typically recommended for street-performance C6s.
Step-9: Install Intermediate Servo Piston Seals
Lubricate and install the seals on the TCI intermediate band servo piston.
Step-10: Install O-Ring & Gasket
TCI servo cover receives its O-ring seal along with a gasket that goes between the cover and main case.
Step-11: Assemble Cover & Piston
Servo cover and piston are mated and ready for installation.
Step-12: Install Cover & Piston
Install the TCI servo cover and piston, taking extra care to not damage seals going in. Get cover and piston square with the case and gently press into place. Torque is 12 to 20 ft-lbs.
Step-13: Adjust Intermediate Band
Torque the intermediate band adjustment with 10 ft-lbs, then back off 11⁄2 turns. Hold the adjustment stud and tighten the locknut 35 to 40 ft-lbs.
Step-14: Air-Check Clutches & Servos
All transmissions built by Tom’s Transmissions get an aircheck that includes clutches and band servos.
Step-15: Install Tailshaft Sleeve
The tailshaft housing gets a new TCI sleeve. Pay close attention to the sleeve drain-hole location, which must line up with the casting provision.
Step-16: Install Valve Body
With close attention to manual shift and kickdown levers, install the valve body.
Step-17: Check Valve Body Function
Although the governor has already been installed, here is how to check valve body function through the governor passage at the tailshaft.
Step-1: Inspect Throttle Valve
The throttle valve, which is actuated by the vacuumoperated throttle valve assembly (vacuum modulator). Check for a clean fit and lubricate with transmission fluid before installation.
Step-2: Install Throttle Valve
Next install the throttle valve assembly and pin. This is a press-in throttle valve with bracket common from 1972-on. (Prior to 1972, a screw-in throttle valve and gasket is used.) Pin lengths tend to vary depending upon application and what you want the transmission to do.
Step-3: Inspect Pan Gaskets
If you’re tired of leaking pan gaskets, pay close attention to pan condition. Warped and distorted pans leak regardless of what you do for a gasket. Pan contact surfaces must be true and void of distortion. If the pan rail cannot be dollied true, replace the pan. Cast aluminum pans offer fluid capacity and cooling capacity. If you must use a steel pan, find one with perfect rails and use a thick, highquality gasket. You could use a super-thin film of Form-Agasket non-hardening sealer on leakers but not everyone agrees with this approach.
Step-4: Transmission Fluid
You don’t have to use Type F in old Ford automatics. It is more old-school with dated friction enhancers. For old Ford automatics today you can use Dexron III or Mercon IV, which are new technology. Torque converters must always receive 1 to 2 quarts for a good pump prime and quick lubrication on start-up.
Step-5: Install Torque Converter
If installed incorrectly, the torque converter can cause pump and converter damage. Carefully work the converter, stator, and input shaft until the converter seats. If you can get your hand between the converter and bellhousing, the converter isn’t properly seated.
TCI-equipped C6 with the improved Low Gear package is ready for action. With the low gear ratio, acceleration is dramatically improved, as is the fierce reliability of E4OD internals and lowfriction benefits of Torrington bearings instead of thrust washers.
Step-6: Install Low-Friction Torrington Bearings (Performance Tip)
One path to a better C6 is to install low-friction Torrington bearings between geartrain stages. Low drag equals better performance at the tailshaft. Torrington bearings handle friction better than those old thrust washers.
Written by George Reid and Republished with Permission of CarTech Inc