Although it is widely believed shift improvement kits are for improving performance, they are also about improving durability. A soft upshift, particularly at WOT, is caused by clutch and band slippage, which generates heat and puts excessive friction material in the fluid. Friction material and metal particulates damage seals and moving parts. As seals wear, line pressure deteriorates, causing more slippage and heat. Heat tends to cook the fluid, doing further damage.
This Tech Tip is From the Full Book, FORD AOD TRANSMISSIONS: REBUILDING AND MODIFYING THE AOD, AODE AND 4R70W. For a comprehensive guide on this entire subject you can visit this link:
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For the street, you want a firmupshift without heat and slippage that doesn’t jar your teeth out. A firm, seamless upshift indicates quick, solid band and clutch engagement.
There are many shift improvement kits in the marketplace, including those that come with overhaul kits custom tailored to the kind of driving you intend to do.
Because Tom’s Transmissions used a TCI Automotive transmission over-haul kit in Chapter 4, it was decided to use TCI Automotive’s Trans-Scat kit for the 1980–1993 Ford AOD (PN 436000).
TCI Automotive offers three Trans-Scat kits for the AOD: Street, Street/Strip, and Heavy Duty. These are commonsense shift improvement kits designed to improve line pressure and control, thereby improving shifts with solid clutch and band engagement.
The street version delivers a firmer upshift than stock, improving durability.
They build the street/Strip Trans-Scat into every Street Fighter transmission for tire-barking firm upshifts. This means no slippage, better transmission of power, and increased durability.
The heavy-duty version is for severe-duty use in police, taxi, and towing applications where you get a firm, but not harsh, shift.
This kit can be installed on a workbench, where everything is easy to see and understand, rather than on a lift. As the valve body is disassembled, note where parts go via the use of a good digital camera to capture the valve body as it is prior to disassembly. Be sure you capture even the smallest detail as each segment is disassembled.
The valve body should be completely disassembled with every part laid out on a clean surface in the order they came out of the valve body. Once completely disassembled, the valve body and each component should be cleaned in a solvent with a high evaporative rate or hot solvent washer to remove any sludge or debris. Then valve parts, including seals, should be soaked in automatic transmission fluid and reassembled.
Some transmission technicians suggest washing the valve body before valve parts are removed to minimize the risk of faulty reassembly, although a completely disassembled valve body with all parts removed is easier to clean internally.
Dropping a transmission pan and examining the fluid is a good way to learn about the transmission fluid condition, which immediately determines transmission health. Transmission fluid should be red/pink and clean. If it is brown or black, it is burned and the transmission should be left alone until a rebuild can be performed.
Take pictures of the valve body before it is removed. Observe the positioning of the manual and throttle valves. When it is time to split the valve body and separator plate, make sure the valve body is flat on the bench with the plate facing up. You don’t want to lose any of the balls, check valves, or hardware.
Valve Body Disassembly
Step 1: Disassemble Valve Body
The valve body is disassembled and carefully laid out on a clean workbench. It is a good idea to take pictures as you go to ensure parts go in the way they came out. TCI provides detailed instructions with the kit (PN 436000). Take careful notes of where fasteners, balls, and valve parts go.
Step 2: Note Check Ball Locations (Documentation Required )
This disassembled AOD valve body clearly demonstrates where the check balls go (arrows). When you remove the valve body’s separator plate, be careful not to spill the ball check valves before shooting an image of where they go.
Step 3: Remove Valves
Brian Fortune of Tom’s Transmissions removes each check valve, taking note of location. Even savvy transmission builders must take note of where the check balls go because there are endless variations.
Step 4: Wash Valve Body in Solvent
The valve body is washed with an environmentally friendly solvent and then a high-evaporative solvent to dry it out. A high-evaporative solvent, such as brake cleaner or lacquer thinner, removes all debris and moisture for reassembly.
When modifying the separator plate, refer to step 4 on page 79. That illustration also demonstrates how to modify the valve body passages where necessary. Note that orifice “H” in that illustration is a new hole/passage that is not found in your existing separator plate. Gaskets must also be modified where new holes are drilled. Keep in mind not all AOD transmissions are per that illustration, which requires close attention to detail. Very time consuming, but necessary.
When you’ve completed your shift enhancement kit installation, road test it to establish proper operation. While you’re at it, check the line pressure with a pressure gauge. Upshifts should be firm, but not violent. If they are too firm, reduce the TV cable tension in small increments. If there’s a lot of slippage and a soft shift, you don’t have enough line pressure, and there’s a great risk of transmission damage.
Modulator Valve Installation
Step 1: Inspect 1-2 Accumulator Valve and 1-2 Capacity Modulator Valve
These two valve assemblies are on the driver’s side: the 1-2 accumulator valve (A) and the 1-2 capacity modulator valve (B). Both require modification with parts from the Trans-Scat kit.
Step 2: Remove 1-2 Capacity Modulator Valve
Remove the 1-2 capacity modulator valve retaining clip. The valve assembly should pop out. Pay close attention to how this valve and spring go together. Early AODs call for the use of an awl to remove the end plug.
Step 3: Inspect Capacity Modulator Valve Layout
This is the 1-2 capacity modulator valve as installed by Ford, which is a spring and valve piston with an O-ring seal. These parts pop out for easy modification.
Step 4: Inspect Street/Strip Configuration
If you’re using the TCI Street/Strip kit, this is the configuration you want with the 1-2 capacity modulator valve. Cap over the spring (shown) following TCI’s detailed instructions closely.
Step 5: Install Street/Strip 1-2 Capacity Modulator Valve
Once you have the correct configuration, install the 1-2 capacity modulator valve. Note the cap is over the spring. For the Heavy Duty kit, ﬂip the cap so that it isn’t over the spring. This increases the spring tension. Insert the valve piston and install the clip.
Boost Regulator Valve Installation
Step 1: Remove Main Regulator and Pressure Boost Valves
When you remove the main regulator/pressure boost valves be sure to lay them out as installed. This is the boost valve and sleeve. The valve is inside the sleeve.
Step 2: Remove Main Pressure Regulator Valve
This is the main pressure regulator valve, which is tied to the small spring. The large white boost valvespring (inside the valve body) rests against the large washer located on the valve piston.
Step 3: Inspect Main Regulator Pressure and Boost Valvesprings
These are the main regulator pressure spring (small) and boost valvespring (large). With the TCI kit, replace the large boost valvespring with a like spring from the kit.
Step 4: Install TCI Boost Valvespring
Replace the large white boost valvespring with this TCI spring.
Step 5: Reinstall Boost Valve Assembly
With the TCI spring in place, reinstall the main regulator pressure valve, springs, and boost valve. Dip the valve piston in transmission ﬂ uid for installation and ease of movement once installed.
Step 6: Install Boost Valve/Main Pressure Regulator Valve Clip
Install this clip next. Check the valves for freedom of movement. You want to verify the proper valve function (movement) before continuing.
Throttle Valve Installation
Step 1: Remove Throttle Valve Clip
Carefully remove the throttle valve retainer clip, making sure the valve parts are accounted for and laid out. Removal of this clip frees the throttle valve.
Step 2: Remove Throttle Valve (Documentation Required)
Remove the throttle valve assembly and lay it out in proper order. Take note of the throttle valve and all of its related pieces for easy reassembly later.
Step 3: Install Throttle Valve Assembly
This is the throttle valve system as installed in the valve body. From left to right are the throttle sleeve, preload spring, throttle plug, throttle control valve and spring (purple), and the throttle plunger. Replace the throttle control valve spring with the purple TCI spring.
This is the throttle valve assembly completely reinstalled. The throttle valve is spring-loaded against the TV cable or rod, enabling it to return to rest when your foot is off the gas.
Step 1: Make Room for Pin
This passage is drilled with a 7/32-inch bit to make way for the aluminum plug. Use tape on the drill bit as a guide to avoid drilling too far. Drill no farther than the bottom of the passage. The valve body must be thoroughly washed to remove any debris.
Step 2: Install Aluminum Blockage Pin
Seal the passageway with the aluminum pin provided in the kit. It is a good idea to machine the pin before installation to keep debris out of the valve body. You want the pin ﬂ ush with the valve body surface.
Step 3: Ascertain Drill Size (Professional Mechanic Tip)
Mic each of the drill bits, which are included in the TCI kit, to ascertain size before you do any drilling.
Step 4: Choose Passages to be Drilled
This illustration shows where modifications need to be made and in what size. Keep in mind, if you drill out the wrong hole or go too large, you will just have scrap metal and have to replace the separator plate. (Illustration Courtesy TCI Automotive)
Step 5: Drill “A” Passage
Drill the “A” passage to 3/32 inch for the Street/Strip and Heavy Duty kits and 5/64 inch for the Street kit. Slowly and cleanly drill this passage, using transmission ﬂuid as a lubricant. Gently deburr the hole’s ragged edges with a larger bit, then wash the plate in solvent.
Step 6: Drill “D” Passage
This is the “D” hole; drill it to 3/32 inch for the Street/Strip kit, 5/64 inch for the Heavy Duty kit, and not at all for the Street kit. As with the “A” passage, use a lubricant and deburr the hole.
Step 7: Drill “F” Passage
This is the “F” hole; drill it to 7/64 inch for the Street/Strip kit, 3/32 inch for the Heavy Duty kit, and 5/64 inch for the Street kit. Deburr the passage.
Check Valve and Separator Plate Installation
Step 1: Install Check Balls and Valves
The check ball and valve installation calls for close attention to detail, one valve at a time. TCI’s instructions are very specific and easy to read, making this task straight-forward. The check balls reinstall in the same locations.
Step 2: Inspect Check Valve Installation (Critical Inspection)
There are a total of eight check balls and two linear spring-loaded valves. The two spring-loaded valves on the far left are pressure relief valves. The top one is the throttle valve pressure relief valve. The closer valve is the torque converter pressure relief valve with a blue spring. They are not interchangeable.
Step 3: Install Valve Separator Plate and Gaskets
Be absolutely certain the valve body surfaces are hospital clean and all modified holes are clean and free of burrs and debris. Two types of gaskets are used; do not get them mixed up. The the double white–stripe gasket is for 1980–1989 and the red-stripe gasket (shown) is for 1990–1993.
Step 4: Position and Check Separator Plate
Install the separator plate with the red-stripe 1990–1993 gasket. Check all holes/passages for accuracy and alignment. Take care not to lose any of the check balls.
Step 5: Locate and Install Reinforcement Plates
Position the separator plate and reinforcement plates with the bolts installed. The short bolts go in the corners (see step 4 on page 79).
Step 6: Torque Separator and Reinforcement Plates (Torque Fasteners)
Torque the 11 valve body bolts crisscross evenly to 80–120 in-lbs. Be very gentle when torquing these bolts in one-third increments. See step 4 on page 79 for proper bolt placement before tightening them.
Written by George Reid and Posted with Permission of CarTechBooks