April 2020 – Gearstar

You can upgrade your Ford C6 transmission to ensure it can meet the modern-day expectation of performance and toughness. This may be a classic ride, but the mere fact that it was built to offer long term durability means it can be revamped to handle whatever you throw at it. To think that this transmission was once built for the most powerful Ford engines back in the 1970s and specifically high-performance sedans and Mustangs, a lot can be expected after its rebuild.

Therefore, the outcome is quite promising since you already have something solid to work with. You only need to find the best parts out there that can take this transmission’s performance one step further to ensure you get the best horsepower. Read on and we’ll show you how to make your C6 transmission rugged enough to offer more impressive performance.

Overview of the Ford C6 Transmission

For the uninitiated, the Ford C6 was designed by Ford Motor Company and it was prevalent between 1966 and 1996. This is a heavy-duty three-speed automatic transmission and upon its launch, Ford marketed it as the SelectShift Cruise-O-Matic.

The Ford C6 featured a less complex build, lighter weight, greater torque capacity, and less power loss compared to its predecessor, the MX transmission. These capabilities were achieved without a larger build compared to the design of its predecessor.

Interestingly, the C6 was also the first automatic transmission built to be compatible with the Borg-Warner flexible shift band in a bid to improve its service life and durability. Cars that used the C6 transmission include the:

- 1978–1991 Ford Bronco
- 1967–1996 Ford F-Series
- 1964–1970 Ford Fairlane
- 1966-1974 Ford Galaxie
- 1966–1980 Ford LTD
- 1977–1979 Ford LTD II
- 1966–1979 Ford Ranchero
- 1966–1979 Ford Thunderbird
- 1968–1976 Ford Torino
- 1966–1979 Lincoln
- 1966–1969 Mercury Comet
- 1967–1973 Ford Mustang
- 1967–1978 Mercury Cougar
- 1966–1972 Mercury Meteor
- 1968–1976 Mercury Montego
- 1968–1974 Mercury Monterey
- 1977 Mustang Cobra 2

Accordingly, if your ride falls among this list, let’s show you how to upgrade your C6 transmission to handle the challenges it’ll face while gliding on a modern road. It may be a transmission used in classic cars, but it can still be a ride you’ll enjoy cruising around town.

How to Upgrade Your Ford C6 Transmission

You can try the following to beef up the performance of your C6 transmission:

1. Custom Parts

The C6 transmission boasts of being lighter than the MX transmission, however, it still has a lot of weight when it is not compared side-by-side with its predecessor. The effect of this heavyweight is seen in the loss of horsepower as parts and pieces of the transmission try to turn.

On the other hand, combining custom parts with certain C6 components can help to reduce the loss of horsepower. In line with that, a modern 4R100 electronic-overdrive can also be paired with this mix to ensure the transmission can withstand high impacts it will be susceptible to.

2. Valve Body Upgrades

The valve body of your C6 transmission can also be upgraded to enable automatic shifting. A valve body shift kit also comes with the promise of giving firmer shifts and can eliminate problems such as band failure, clutch chatter, and premature clutch.

And while at it, a trans-brake can be installed which will be most appreciated if you’re a drag racer. Another consideration is the use of thicker high-performance bands or optionally settling for a deeper oil pan.

3. Bell Housings

The stock case can be mounted with an SFI-certified bell housing, which could push the horsepower even further. If you’ll like a clearer picture of what to expect, then that horsepower may be around 1,000 hp, 2,000 hp, or more.

4. C6 Planetary Carriers

Switching to C6 planetary carriers that are stronger can also improve the performance of your transmission. Here, the new planetaries can surge the transmission’s horsepower to over 2000 hp, and the latter can be expected if a change has been made to the input shaft.

What’s more, the clutch packs can provide better surface material as well as more clutches to support greater gripping power. Needle bearings are also used to replace thrust bearings in several of the rolling components to reduce friction.

5. First and Reverse Planetary Gearset

There is a three or four pinion unit in the First and Reverse planetary gearset. This unit is made of aluminum and it can be replaced with a six-pinion planetary gearset that is made of steel. An increase in the number of pinions aids in the distribution of load and the change in the material makes the unit stronger.

6. Lincoln Drum

A Lincoln drum can be used in this transmission. This drum has higher snap-ring groove and as such, it can support the installation of more clutches. While the stock Lincoln drum may feature four clutches, up to six clutches can be fitted in it to offer a higher level of grip.

7. Aftermarket Clutches

There are less thicker aftermarket clutches you can rely on instead of the stock clutches. Let’s take for instance a clutch that is 0.0065-inch-thick instead of the stock clutches that is 0.0080-thick. Choosing less thick clutches provides space for stacking.

8. Gear Ratios

The C6 transmission comes with First, Second, and Third gear ratios that are 2.40:1, 1.40:1, and 1:1 respectively. Nonetheless, a wide-ratio gearset can be used to provide a First gear ratio that is numerically larger.

The result will be 2.72:1 and 1.54:1 for the first gear and second gear, respectively. Opting for a higher first gear ratio would be especially beneficial if you have a heavy car, which makes the gear act faster and there’s no increase in the driving RPM.

The Bottom Line

These are the tips you can use to upgrade your Ford C6 transmission and give it that level of performance you believe it can achieve. What’s more, you get to know about the transmission you’re using and why it is a good choice for an upgrade of this type. For starters, it was built with the intention to be tough hence the foundation was set already.

Nonetheless, you can fall back on the expertise of a professional to help you out if you’re uncertain about how to carry out these upgrades yourself. Give or take, you’ll spend a few hundred bucks in a transmission repair shop, which will save you from ruining your transmission while on a quest to experiment.

Improving the performance of your 700R4 rebuild comes with a basket-full of benefits. For starters…

An upgrade will make your transmission powerful enough to handle drag racing, while at the same time offering an enjoyable driving experience around town. This is because there will be minimal or nonexistent sluggishness in shifts to impact on power.

On the other hand, it’s worth noting that you have the choice of changing the transmission entirely. But we all know how expensive a change can be, hence, upping the performance is a cheaper alternative to getting a more enhanced performance.

Therefore, if you have a 700R4 rebuild and you’re ready to give it a boost that will result in high-level performance, work with us and we’ll show you how to get started. But get this first!
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Modern vs. Automatic Transmissions

Unarguably, modern overdrive transmissions are controlled by computers, which differs from older automatics like the 700R4 that rely on a valve body to be mechanically controlled. It, therefore, follows that a change in certain parts of the valve body can improve its performance. It’ll be able to provide firmer shifts, while at the same time-saving power.

Accordingly, one major part of the 700R4 valve body you’ll want to focus on is its TV cable, since this transmission may be damaged as a result of a poorly adjusted TV cable. The TV cable helps in adjusting the internal line pressure as well as part throttle shifting

A TCI Automotive Constant Pressure Valve Body kit can help you to work on the TV cable. What the TCI system does is to add parts that will maintain the accurate line pressure every time, and this means there’s no need to struggle in making a perfect adjustment to the TV cable.

Another kit that may prove useful is a lockup wiring kit. This kit offers two possible options where you can either lockup the converter manually whenever you want, or lockup the converter while in Fourth gear, automatically. Now pair these kits with a powerful torque converter and you’ll be able to turn even the most sluggish 700R4 rebuild into a faster and more powerful transmission.
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Boosting the Performance of Your 700R4 Rebuild

Here are the simple steps that will help you to improve the performance of your 700R4 rebuild:

1. Take Off the Pan and Filter

You need to take off the pan on the 700R4 to expose the large flat filter beneath it. You can then proceed to remove the filter and its seal before disposing of both. Once the filter is off, you’ll be presented with the valve body. This component controls the shifting of the transmission.

2. Remove the 1-2 Accumulator

Take off the 1-2 accumulator by unloosening the bolts that secure it in place. These bolts are to be separated from others since they are unique to the accumulator.

3. Remove the Auxiliary Valve Body

The next step is to take out the auxiliary valve body while ensuring that the stock check valve is not lost because you’ll still have a need for it.

4. Unbolt and Remove the Throttle Pressure Mechanism

Proceed to unbolt the throttle pressure mechanism and then remove the component. Also, the wire cable linkage should be disconnected as the mechanism is pulled up and the bolt securing the detent roller spring assembly is disengaged.

5. Remove the Valve Body Bolts

Any leftover valve body bolts can now be removed. Next, the valve body, gasket, and separator plate can be taken off of the transmission. This will also enable you to remove the 3-4 accumulator piston and piston pin.

Both of these are situated beneath the region where the 1-2 accumulator was taken out of. And worthy of note, is to pay attention to the balls in the valve body, which may fall out in case you don’t have spares to serve as a replacement during reassembly.

6. Remove the Pressure Regulator

The transmission pump has a pressure regulator, and this component needs to be removed as well. Here, apply pressure downwards on the TV boost valve sleeve and use snap ring pliers to remove the retaining ring. Proceed to remove the TV boost valve sleeve, valve, and the reverse boost sleeve. What you’ll have is the top rows parts coming out where the lower row features the TCI parts.

7. Choose Spring Type

You can either use a silver spring to have a firm-style shift or attach the shim to the silver spring to get a street/strip-style shift. Another spring option is a gold spring without the shim and this offers hard shifts.

After the disassembly, you’ll notice some check balls from the stock valve body. These are reusable 1/4-inch silver ones that are four in number. There’s also a check ball in copper color and this may not be reused.

The TCI kit comes with spare check balls to ensure you can replace it if the original gets missing. You can then use the TCI instructions to reinsert the check balls while using some grease to hold them in place.

8. Insert a New Separator Plate and Gasket

A new separator plate looks similar but is still a bit different from the stock that came with the transmission. You can insert the new separator plate and gasket into the transmission, but it might be needful to modify the 3-4 accumulator using a self-tapping 1/4-inch x 20 Allen head plug. The accumulator piston and spring can also be replaced without using the black spacer.

9. Install the New TCI Valve Body

And after installing the gasket/plate assembly, it’s time to install the new TCI valve body. The rod for the valve body linkage can then be attached while ensuring that the valve is not forced and neither is the linkage bent.

10. Reinstall the Solenoid and Transmission Wiring

Also using the TCI instruction, reinstall the solenoid and transmission wiring. While at it, it may be useful to include a TCI lockup wiring kit to enable the torque converter clutch to enable flexible engagement of the automatic activation of the torque converter clutch in Fourth gear. This setup will also allow the clutch to disengage during acceleration or downshifts.

11. Reinstall the 1-2 Accumulator Assembly

The 1-2 accumulator assembly can be reinstalled after the piston has been mounted within the housing using a large orange TCI spring. The black spacer can also be installed if your ride is meant for street/strip applications. You can then fasten the bolts to 8 ft-lb.

12. Reinstall the Throttle Pressure Mechanism

It’s time to reinstall the throttle pressure mechanism and also the cable linkage while ensuring that the latter is well placed on the large lever. Other steps include running new wires, inputting oil pipe and tightening the bolts of the valve body to 8 ft-lb. In contrast, the detent roller spring bolt can be tightened to 10 ft-lb.

13. Replace the Filter

The TCI kit also comes with a filter seal ring and a new filter that you can use to replace the old one that was disposed of.

14. Revamp the Transmission’s Exterior

You can also revamp the exterior of the transmission by working on the servo. The parts of the stock servo can be replaced with the TCI parts before reassembling.
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The Bottom Line

These are the easy steps to up the performance of your 700R4 rebuild without spending the extra cash to buy a new transmission. While these are DIY steps, you can employ the services of a professional if you’re unable to handle these procedures yourself. It’ll ensure that the transmission rebuild is just right and you don’t have a worse transmission than what you started off with.