Automatic transmission function, in theory, is simple. In practice, it is quite complex and has been worked out by powertrain engineers determined to give you smooth and reliable operation for at least 100,000 miles. To get there, you have to have a hydraulic control system that gives you all those things you want and expect from a C6 automatic transmission. You want a firm upshift, yet you also want a downshift during coast and deceleration that cannot be felt. And when you punch the accelerator, you want a quick and positive downshift that delivers rapid acceleration without delay. That’s a lot to expect from one of the greatest feats of mechanical engineering in automotive history. And it has only improved in the years since those old iron automatics were new.
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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When companies like TCI Automotive develop shift modification kits like the Trans-Scat valve body kit, a lot of thought, research, and development has to go into that kit. And this is something you don’t take lightly because of what you want from an automatic transmission.
TCI Automotive offers two Trans-Scat options for the Ford C6: Towing or Competition. In both cases, the Trans-Scat kit gives you a firm upshift, which is nothing more than solid clutch-and-band engagement to eliminate slippage. Stock automatic transmissions deliver a soft shift because most people generally don’t want to feel the upshift. To get a soft shift, there has to be clutch and band slippage, which means slippage is programmed into valve body design.
Slippage comes from the gradual engagement of clutches and bands for a soft shift, which causes heat and the release of friction material into the transmission fluid. This is what drivers generally want from their automatics—a soft, unnoticeable shift, which is a product of slippage. Friction material in the fluid from slippage damages seals, which hinders line pressure and causes additional slippage and transmission failure.
There’s more to the C6 Trans- Scat kit than just performance. It is all about giving your C6 longevity because this kit gets rid of destructive slippage. A firm upshift means no slippage, better performance, and longer transmission life.
Installing a TCI Trans-Scat
So what happens when you install a shift modification kit? Without becoming too technical here, a shift modification kit changes line pressure and timing to produce a firm up shift, mostly at wide-open throttle. It also delivers a firmer shift under normal driving conditions. Instead of gradual applications of hydraulic pressure to clutches and band servos, pressure arrives more quickly and firmly, which prevents slippage. It is not only about increased line pressure, but the all important timing.
Step-1: Remove Filter
Valve body disassembly begins with filter removal and disposal. You’re going to need 3/8- and 5/16-inch sockets.
Step-2: Remove Valve Body Bolts (Documentation Required)
C6 valve body consists of two halves. Remove remaining bolts with a 3/8-inch socket. Before you separate the halves, remember to inspect the check balls and two spring-loaded valve assemblies. As you carefully separate the halves, take note of check ball and valve locations.
Step-3: Note Position
You want the larger upper half on top when the halves come apart.
Step-4: Remove Relief Valves & Springs
Both the drain-back valve and converter pressure-relief valve look like this and are located in the valve body. Carefully remove and reinstall the springs and valve discs in the same locations.
Step-5: Remove Separator Plate
Next remove the separator plate from the upper half of the valve body.
Step-6: Examine Valve Body (Critical Inspection)
When you closely examine the C6 valve body’s lower half, it appears very complex. Actually, each passage and valve performs a specific function, channeling line pressure to clutches and the intermediate band servo. Although check balls and valves are not shown here, you need to know where they’re located.
Step-7: Wash Valve Body
Wash the valve body using a petroleum- based solvent. Never use a water-based solvent. Water aggravates corrosion between steel and aluminum parts.
Step-8: Note Pressure Boost Valve
Trans-Scat installation begins at the pressure boost valve. This is the stock configuration. Early C6 valve bodies have a retainer plate with two screws removed with a 5/16-inch socket. Later versions don’t have this plate, but instead a retainer clip that holds the pressure boost valve, sleeve, springs, and main pressure regulator valve. In any case, be prepared for a spring-loaded assembly where parts can be lost on release.
Step-9: Use Correct Spring
This application calls for the 1975-on orange pressure-regulator spring with no other changes. The orange spring has more tension than the blue one.
Step-10: Install Pressure Boost Valve
The entire assembly goes back in and ends with the sleeve and pressure boost valve shown here. After this valve package is flush, reinstall the retaining clip or plate depending on model year. Always check for freedom of valve movement before continuing.
Step-11: Remove Long End Plate
Using a 5/16-inch socket, remove the long end plate. There are seven different valves located here and they demand your close attention to detail.
Step-12: Install Servo Modulator Valve
Next is the intermediate servo modulator valve. The factory installed a spring here to modulate servo pressure.
Step-13: Replace Spring With Plug
TCI eliminates this spring and goes with a plug, which cannot stick out of the valve body. If it does, it must be ground down to where it is flush or below deck. If you must grind the plug, clean and deburr it before installation.
Step-14: Remove Servo Accumulator Valvespring
Next in line is the intermediate servo accumulator valve. This can be confusing because the intermediate servo accumulator valve is fitted with one spring early in production and two later on. This 1975 C6 valve body has one spring, which adds to the confusion. Replace this spring with the natural-metal spring from the kit. There’s less spring tension from this TCI spring.
Step-15: Make Modifications (If Applicable)
Changes need to be made to the cut-back valve if you’re building for high-performance street/strip. Remove cut-back valve in this bore and replace with a 1/4-inch check ball. Then reinstall cut-back valve. For severe duty/towing, no modifications are required here.
Valve Body Reassembly
Step-1: Reinstall Long Plate
Reinstall the long-end plate, using a 5/16-inch socket. Torque is 20 to 30 in-lbs. After installed, make sure all valves have freedom of movement.
Step-2: Remove Short End Plate
Remove this smaller end plate next, using a 5/16-inch socket to expose throttle boost and manual-low 2-1 scheduling valves.
Step-3: Remove Valve & Spring
The throttle boost and manual-low 2-1 scheduling valves are both shown here. Throttle boost valve is installed in the valve body. Remove only the manual-low 2-1 scheduling valve and spring.
Step-4: Replace Spring
Swap out the manual-low 2-1 scheduling valve spring with the violet spring from your TCI kit. Reinstall the manuallow 2-1 scheduling valve and spring and the end plate. Torque is 20 to 30 in-lbs.
Step-5: Note Proper Drilling Locations
TCI instructions include a template, which shows you where to drill, using the 1/8-inch bit included in the kit.
Step-6: Drill in Appropriate Locations
Using your C6’s old separator plate, compare it with the illustration in your TCI instructions One of these holes lines up with the hole already in your separator plate. Mark the existing hole. Take the TCI separator plate in your Trans- Scat kit and mark the position of the hole from your existing separator plate. Take the 1/8-inch drill bit and drill the new hole in your new TCI separator plate. Discard the old plate. Deburr the hole with a larger bit.
Step-7: Reassemble Upper Half
Reassembley the upper half of your C6 valve body with new gaskets from the TCI kit. Bolt torque is 20 to 30 in-lbs.
Step-8: Install Check Balls
Check ball installation is next. Look for round pockets to ascertain location. This is the 1/4-inch-diameter throttlepressure relief ball and spring.
Step-9: Install Disc & Spring
The torque-converter pressure-relief valve disc and spring. Nearby is the 2-3-shift check valve and spring, which look like this valve—you don’t want to get the two mixed up.
Step-10: Assemble Valve Body
Two valve body halves go back together. Torque is 20 to 30 in-lbs. Valve body is ready for installation. Don’t forget the filter.
Written by George Reid and Republished with Permission of CarTech Inc