The objective of this chapter is to show you how to improve the AOD’s durability and performance with the best parts and improved shift programming. Because the AOD’s geartrain is based on the FMX, FX, and MX transmissions, it has proven to be reliable, with generations of refinement leading up to what is now a very rugged transmission.
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:
SHARE THIS ARTICLE: Please feel free to share this article on Facebook, in Forums, or with any Clubs you participate in. You can copy and paste this link to share: https://www.diyford.com/ford-aod-transmission-assembly-guide/
You can build a durable AOD using upgraded Ford parts from the late 1980s, or you can step up to AODE/4R70W geartrain components that help improve both performance and durability, especially the AOD’s weakest link, the reverse drum and overdrive band. There are plenty of AODE/4R70W donor cores out there and a wealth of new aftermarket parts engineered to make your AOD world class.
The AOD is covered separately from the AODE in this book because it really is a different transmission, although the basic fundamentals are the same. If you’re building the AOD for performance use, you want AODE/4R70W geartrain components. If you’re building an AOD for your daily commute, you can go with original geartrain components and get the desired durability. The choice boils down to how you want the transmission to perform. If you want improved acceleration, you want the 4R70W’s geartrain with its wide-ratio 1-2-3-4 upshift.
Operation and Power Flow
AOD operation begins with a six-position shifter marked P-R-N-D(OD)-D-1. These ranges are park, reverse, neutral, drive/overdrive, drive (without overdrive), and first. Beginning in 1991, the AOD couldn’t be placed in gear without a foot on the brake pedal.
When the selector is placed in drive/overdrive, a normal 1-2-3-4 upshift pattern occurs, with overdrive/lockup taking place at around 40 mph. The drive/overdrive position is a fully automatic operation. Slip the selector into “D” and you get 1-2-3 upshifts without overdrive or fourth gear. Start out in “1” and you get a 1-2 upshift, but no higher.
As acceleration begins from a stop, fluid under pressure flows through the torque converter in the conventional manner via impeller, stator, and turbine. Anytime the converter is multiplying torque, which happens under all acceleration, however light, fluid temperature increases because there is an increase in pressure and resistance to fluid flow. As fluid temperature increases, viscosity changes and shift quality/function changes.
Fluid under pressure flows first through the outer hollow input shaft during torque multiplication (acceleration and light throttle) and into the geartrain in ranges 1-2-3 and reverse. In overdrive, pressure is channeled from the torque converter shell directly to the overdrive unit via the solid inner shaft, bypassing the torque converter function completely. It feels like a manual transmission in overdrive because there is no slippage or torque multiplication. This process is referred to as “split torque” because fluid flows via torque multiplication (on the torque converter) under acceleration into the geartrain through the smaller input shaft and straight drive when the transmission is in overdrive.
The Ford AOD is different from most automatic overdrive transmissions because it does not have a locking torque converter. Instead, it has a locking overdrive unit driven by the smaller secondary input shaft within the main input shaft. The AOD also differs in that overdrive isn’t an afterthought; it’s incorporated into the existing geartrain rather than being a bolt-on. It is a true 4-speed automatic overdrive transmission.
In “D/OD,” which is fully automatic, the AOD performs a 1-2-3-4 upshift as vehicle speed increases. At 40 mph, the AOD is designed to shift into overdrive lockup on the smaller input shaft into the direct clutch. There are two types of throttle valve control systems used with the AOD. The 3.8L Essex V-6 and 5.8L (351-ci) Windsor V-8 employ a control-rod throttle valve modulation system without a vacuum modulator. The 5.0L (302-ci) V-8 engine uses a TV cable system.
The throttle valve shift modulation system does what the vacuum modulator and throttle kickdown linkage did with the C4, C6, and FMX transmissions. The throttle valve system controls line pressure and shift-points based on throttle position only.
Internal Components Installation
Step 1: Inspect Kit Parts
A complete AOD overhaul kit from TCI Automotive includes fresh clutch frictions and steel plates, along with gaskets, seals, and a new filter. These items, coupled with AODE/4R70W hard parts such as bearings, bushings, and thrust washers from TCI, make the AOD ready for real power.
Step 2: Install New Bushings and Seals
Install a new bushing and seal in the tailshaft housing. Remember, some seals incorporate a lip spring. Pack wheel bearing grease around the spring to keep it in place during installation.
Step 3: Install Front Pump Seal
Assemble the front pump with a new seal and bushing. The seal should be packed with assembly lube to prevent lip spring loss. The bushing should also receive generous amounts of assembly lube.
Step 4: Fill Pump Cavity with Transmission Fluid
For a good pump prime and plenty of lube, fill the AOD’s front pump cavity with transmission fluid. When you fill the pump cavity with solid assembly lube or transmission fluid, you get plenty of lubrication and line pressure with the initial start-up.
Step 5: Orient Pump Gears
The front pump is a gear type, which provides a steady, uninterrupted flow of fluid under pressure. There are two gears: the drive gear (inner) and the driven gear (outer). The inner drive gear must be installed with the open side toward the torque converter. Get this backward and the torque converter does not seat/engage into the pump. The chamfered sides of both gears face into the pump housing.
Step 6: Install Front Pump (Torque Fasteners)
The back half of the pump housing is mated to the stator support half. Torque the bolts to 12 to 16 ft-lbs. The transmission side of the pump fits only one way.
Step 7: Assemble Intermediate Clutch Cylinder
The intermediate clutch piston fits into the pump housing, which doubles as a clutch pack for all those clutches in front. Proper clutch piston seal installation is crucial. Some seals have lips that must be angled where they seal against the piston and bore from the pressure side. Get this backward and it cannot seal.
Step 8: Install Intermediate Clutch Piston
Perform the intermediate clutch piston installation with great care to protect the inner and outer seals. Use a seal lip manipulation tool with a close eye on the seal status. Seal distortion or tearing is unacceptable.
Step 9: Install Front Pump Seal
Use plenty of transmission assembly lube to install the pump perimeter seal. Transmission assembly lube is compatible with transmission fluid. Always use an assembly lubricant that works with transmission fluid.
Step 10: Install Pump Sealing Rings
Carefully install the iron pump seal rings. They are very specific in function and location. The reverse clutch sealing rings are closest to the pump’s main cavity. The forward clutch sealing rings are near the end of the clutch support. These rings all contain line pressure much like an engine piston ring contains cylinder pressures. The ends are gapless, which means they interlock.
Step 11: Install Forward Clutch Piston Seals
Install the forward clutch piston inner and outer seals with liberal lubrication to prevent seal damage and distortion. The seal lip must be pointed toward the pressure source, away from the clutches to be effective. Get this backward and the seals do not hold pressure.
Step 12: Install Forward Clutch Piston (Special Tool)
Use the seal protection tool to install the clutch piston so the seals glide in smoothly. This tool helps prevent seal damage. Other types of installation tools are available. The key to success is watching the clutch seals carefully as you go.
Step 13: Install Forward Clutch Piston Return Springs
Use a C-clip retainer with the clutch piston return spring. This is an AODE/ 4R70W forward clutch drum, which is stamped steel instead of iron, and it has a single return spring.
Step 14: Load Forward Clutch Frictions and Steels
It’s time to load the forward clutch with steels and frictions. Begin with the wavy plate at the clutch piston, then load clutch discs and plates alternately.
Step 15: Install Forward Clutch Steels and Frictions
Install the clutch discs and plates alternately until you arrive at the clutch pressure plate. Soak the clutch discs in transmission fluid before installation as fluid affects clutch thickness and clearances.
Step 16: Check Forward Clutch Clearances
Load the pressure plate after all frictions and steels are in. Clearances should be .050 to .089 inch for V-8s and .040 to .071 inch for V-6s between the pressure plate and the first disc.
Step 17: Choose Snap-Ring Thicknesses
Snap rings of different thicknesses are available from transmission supply houses if clearances are not within specifications. Snap rings are of different thicknesses to yield desired clearances.
Faults and Fixes
The AOD wasn’t always as durable as it was near the end of production in the early 1990s. In the beginning, the AOD was prone to failure and didn’t tolerate the power of high-performance engines. By 1989, the AOD was on top of its game as a rugged, reliable overdrive thanks to engineering upgrades that made it more dependable. The AOD’s weaknesses are as follows:
- The direct clutch didn’t have a sufficient number of clutches and steel plates to handle the amount of power Ford put into it with the 5.0L high-output engines that first arrived in the early 1980s.
- The overdrive band and reverse drum weren’t wide enough to handle the load because there wasn’t enough surface area. Both became wider on later models to better handle the load.
- The AOD had insufficient line pressure to both the direct clutch and overdrive band during hard acceleration. Although it appears to be an engineered failure,
- it was Ford’s intent to reduce pump load and improve fuel economy. Unfortunately, this turn of events occurred at the 2-3 upshift, which caused clutch and band slippage, along with destructive heat.
- Irregular line pressure was hard on both the direct and forward clutches. Line pressure was low when it needed to be high and vice versa, causing jerky operation. Much of this was based on efforts to improve emissions and fuel economy. You want high line pressure (control pressure) at WOT for firm upshifts and low line pressure during deceleration so you don’t feel the downshifts with decreasing vehicle speed.
- Split-torque function causes a lot of frustration and durability issues. Although it’s impossible to do away with the split-torque function, it can be improved with modifications to the valve body.
- The AOD was originally developed for light-duty applications, not high-performance V-8 engines. As a result, AODs in Mustang and LTD High Output applications struggled to stay together. As time went on, Ford engineered refinements to the AOD to improve durability.
AOD Clutch Pack Installation
Step 1: Assemble Direct Clutch
Install the direct clutch piston seals. As with the forward clutch, some seal lips are one-direction fit only. Pay very close attention. The seal lips point toward the pressure side. (The blue grease here is transmission assembly lube.)
Step 2: Assemble Direct Clutch Assembly
Step 3: Install Direct Clutch Piston
Press the direct clutch piston into place using seal protectors to safeguard the piston seals. Seal protectors are available from most automatic transmission parts supply houses.
Step 4: Install Direct Clutch Piston Return Spring
Use a compressor to install the direct clutch piston return spring assembly. At home, you can use four C-clamps from a hardware store. Protect your eyes and face.
Step 5: Check Clutch Steel Thicknesses (Precision Measurement)
Clutch plates can be of varying thicknesses. They wear at different rates, which is why thickness can vary. Also, clutch plates don’t always come from the same sources, which affects thickness. Each steel plate should be measured with calipers prior to installation. Do the same with clutch discs after you saturate them in fluid.
Step 6: Install Direct Clutch Thrust Bearing
The direct clutch needs a thrust bearing if you’re going with an original AOD geartrain. AOD transmissions with an AODE/4R70W geartrain upgrade have Torrington bearings instead of thrusts.
Step 7: Install Direct Clutch Hub
The direct clutch needs this clutch hub, which splines into the clutch frictions. Exam-ine the teeth for scoring and other types of damage. Make sure the clutch teeth slide smoothly in this hub.
Step 8: Install Direct Clutch Steels and Frictions
The direct clutch discs and plates drop in alternately. Clearances are .040 to .057 inch for V-6s and .050 to .067 inch for V-8s. Measure the clearances between the pressure plate and the first disc.
You can improve clutch pack durability with a combination of larger-capacity direct and forward clutches by either performing modifications to your existing clutch drums, or by opting for the aftermarket. A trusted machine shop can cut a new groove for the snap ring that allows you to add clutch friction and steel plates.
Another solution is the E8LY-7F283-A direct clutch drum first used in the AOD in 1988, which accommodates one addi tional clutch disc and plate, for a total of six clutches. There is also a vast selection in the performance transmission aftermarket for Ford’s AOD, where you can stuff seven and eight clutches into the direct clutch.
AODE/4R70W Clutch Pack Installation
Step 1: Install Direct Clutch
The AODE/4R70W direct clutch assembles the same way as the AOD. The clutch piston goes in first, with seal lips pointed toward the clutch cylinder and away from the clutches and plates.
Step 2: Use Spring Compressor or C-Clamp (Precision Measurement)
You can use a spring compressor to compress the clutch piston return spring (shown). You may also use C-clamps. A C-clip holds the springs and clutch piston in place.
Step 3: Install Thrust Bearing
The Torrington bearing is also known as the number-7 needle bearing. It has a support ring, and must be installed first.
Step 4: Inspect and Install Direct Clutch Hub
The direct clutch hub sits in the center of the direct clutch drum. The clutch hub should be checked for irregularities that may hinder clutch friction movement.
Step 5: Install Direct Clutch Discs and Plates
Drop the direct clutch discs and plates into the clutch cylinder. Install the snap ring and check clearances. Clearances with the AODE/4R70W direct clutch should be .060 to .091 inch between discs and plates.
Step 6: Apply Assembly Lube
Install the direct clutch Torrington bearing and use liberal amounts of assembly lube. The direct clutch seats in the ring gear/output shaft assembly.
Building a Better AOD
While you’re thinking about performance upgrades, don’t forget basic improvements such as bushings, thrusts, and bearings. Hard parts are rugged and can typically survive several overhauls. However, transmissions that have been sorely neglected can wind up with hard parts that are little more than recyclable metal due to dirty fluid and extreme wear. Reusing worn hard parts can lead to premature transmission failure because the same problem will persist.
Hard parts such as the planet carrier should be closely inspected for unusual wear. Planet gears should feel solid with no wobble, indicating acceptable inside gear and bushing wear. They should also show wear and not have a mirror finish, which is typically excessive wear. Planet and sun gears need to fit one another with great precision or they wear out prematurely.
When clutch drums are disassembled, they should be closely inspected for burred and ragged clutch plate grooves that can hang up clutch discs and steel plates, causing a malfunction. Seal contact surfaces should be true and free from scoring. Rough surfaces should be dressed until smooth and serviceable. Examine clutch pistons for scoring and irregularities that can damage seals.
Output Shaft and Direct Clutch Assembly
Step 1: Install Output Shaft Sealing Rings
Install the number-5 and number-6 output shaft sealing rings. Color and type are important for proper installation and leakage prevention. Beige sealing rings (shown) are for the output shaft and direct clutch.
Install the number-7 through number-10 output shaft sealing rings. The ring gear has already been fitted.
Step 2: Install Direct Clutch Assembly
The direct clutch slips inside the ring gear onto the output shaft where those beige sealing rings are. Make sure you have lubed everything for smooth assembly and function.
The direct clutch has to be twisted and finessed into the ring gear and onto the output shaft. Again, everything must have generous amounts of lubrication.
Assembling clutch packs and other subassemblies requires the detail of neurosurgery because it is so easy to make a mistake when installing seals, snap rings, and clutches. Because seals tear and distort easily, they need genzerous amounts of lubrication.
Some seals are designed to install in one direction only. If you’re working with a clutch piston seal with a lip, the lip must be pointed toward the pressure source or inside the clutch cylinder. With the lip pointed toward the pressure source, you get a fail-safe installation because pressure holds the seal lip against the sealing surface. Installing a directional clutch piston seal backward means leakage and the absence of clutch function from pressure loss.
Regardless of the type of clutch piston seal you are working with, there must be solid contact between the seal, piston, and cylinder.
The intermediate clutches stacked in front of the case can be upgraded by using some of the AODE/4R70W intermediate clutches, which adds clutch capacity. You should use the F3LY-7B006-A clutch plate in place of the stock AOD intermediate clutch plate. This plate provides room for more intermediate clutch frictions.
Another modification is enlarging the forward clutch apply orifice in the valve body’s separator plate, which improves the quality of the 4-3 down-shift. You can make dramatic improvements with genuine off-the-shelf Ford parts. To get durability from the AOD, you have to go to AODE/4R70W inter-nals, which means the entire geartrain from forward clutch to ring gear and output shaft. All of these components are available from Ford parts sources or the aftermarket.
The single greatest improvement you can make is the AODE/4R70W reverse clutch drum and overdrive band. The AOD’s 11⁄2-inch-wide over-drive band doesn’t exhibit enough holding power. The AODE/4R70W’s wider 2-inch band and drum makes a huge difference in durability. You should also use a Kevlar-faced 2-inch overdrive band for extreme-duty service.
Reverse, Intermediate and Forward Clutch Assembly
Step 1: Install Reverse Clutch Apply Piston
Pay close attention to the seal lip direction when you install the reverse clutch piston. The seal lip must be pointed toward the pressure source (toward the cylinder). The seals and piston should have generous lubrication to prevent scoring or distortion. Don’t forget the retaining ring.
Step 2: Install Belleville Spring
The Belleville spring is a clutch piston return spring. Belleville springs tend to split and break, which calls for close attention to detail during disassembly and assembly.
Step 3: Install Apply Plate (Precision Measurement)
Before you install the clutches and plates, install the reverse clutch apply plate. Inspect the pressure plate for scoring and warping.
Step 4: Install Reverse Clutch Frictions and Steels
Alternate reverse clutch frictions with steel plates. Although clutch frictions aren’t wet here, they should be soaked prior to installation to get the proper operating thicknesses so the clearances are right. Not all transmission techs agree with this; however, there’s nothing to be lost by soaking them ahead of time. It is also a good idea to soak clutch friction discs ahead of time for accurate measurement.
Step 5: Install Reverse Clutch Pressure Plate
Install the pressure plate and snap ring last. Check the clutch clearances; they should be .030 to .056 inch for 5.0L V-8s and 3.8L V-6s, or .040 to .075 inch for 5.8L (351-ci) V-8s. Snap rings of varying thicknesses are available to get the clearances right.
Step 6: Install Intermediate Clutch Snap Ring
Secure the intermediate one-way clutch snap ring. Check the one-way clutch for smooth, noise-free operation. It should turn freely in one direction and lock up in the other.
Step 7: Install Forward Clutch and Thrust Bearing
Inspect the clutch grooves and install the forward clutch and thrust bearing. Mate the reverse clutch to the forward clutch and input shaft.
Step 8: Assemble Reverse and Forward Clutches
Stack the reverse clutch drum on top of the forward clutch and input shaft. Seat the reverse clutch drum and check the one-way clutch for freedom of operation.
If your budget allows (this is a very important upgrade), invest in the larger “A” overdrive band servo for solid engagement without slip-page and heat. You should use the 4340 chromemoly input shaft for the AOD, which is available from a number of sources and withstands 700 to 800 hp. One-piece input shafts that combine the inner and outer input shafts bypass the overdrive lockup feature entirely if efficiency isn’t important and performance is everything. It keeps you on the torque converter in torque multiplication mode for crisp acceleration.
Options are available for the AOD performance enthusiast. Len-Tech builds some of the strongest racing automatics in the world, specializing in the AOD, AODE, and 4R70W. One of the AOD’s greatest shortcomings is dual-input shafts (a shaft within a shaft) in a split-torque function. LenTech addresses this issue with a non-locking overdrive, which means the engine stays on the torque multiplication side of the converter for better acceleration even in third gear. You don’t get the efficiency of a direct lockup; however, you do get improved performance.
Case Components Assembly
Step 1: Begin Case Assembly
Install the number-9 Torrington bearing (needle bearing) assembly. Pack the bearing with plenty of transmission assembly lube. All thrust washers and bearings should be new in the interest of durability.
Step 2: Replace Manual and Throttle Valve Shaft Seals
While the case is bare, replace the manual and throttle valve shaft seals and check the shafts for scoring and distortion. Take care to avoid seal distortion and use plenty of lube.
Step 3: Lubricate Manual Shift and Throttle Valve Shafts
The manual shift (left) and throttle valve shaft (right) should be lubricated with transmission assembly lube, then mated and installed in the case.
Step 4: Install Manual Shift and Throttle Valve Shafts
Install the manual and throttle valve shafts with new seals. Position the throttle valve return spring as shown. This is a very tight configuration for an open-end wrench.
Step 5: Inspect Parking Pawl
Here’s the parking pawl actuating rod and cam out of park with the pawl disengaged. The rod and cam should be lubricated with assembly lube.
Step 6: Inspect Parking Pawl CONTINUED
This the parking pawl actuating rod and cam in park with the parking pawl engaged. The cam pushes the parking pawl into the rear gear, locking the output shaft.
From inside the case, you can see that the parking pawl engages the ring gear assembly, locking the output shaft. The parking pawl locks into the ring gear when the selector is placed in park.
LenTech goes beyond the torque converter and geartrain in its quest for performance; it also looks at hydraulics. The factory settings adversely affect performance because upshift tends to occur too early. AOD racers have long known you can upshift from first to third gear and then downshift quickly to first gear before upshifting into third. The transmission stays in second until it is necessary to shift into third.
The problem with this approach is precious lost time and undue stress on the overdrive band and drum. LenTech modifies the AOD valve body, which allows you to upshift normally, 1-2-3-4. LenTech also performs a solenoid overdrive control modification, which allows manual control.
Internal Final Assembly
Step 1: Install Output Shaft and Ring Gear
You install the output shaft, ring gear, and direct clutch assembly as a unit. You can see the direct clutch, which receives the smaller input shaft during final assembly.
Step 2: Install Low-Reverse Band
Position the low-reverse band in the case around the ring gear assembly and locate it on the anchor pins. Make sure it is positioned where the servo actuating rod meets the band. As with clutch discs, the low-reverse band should be lubricated with transmission fluid for installation.
Step 3: Inspect Output Shaft Assembly
With the output shaft, ring gear assembly, direct clutch, and low-reverse band in place, it becomes clear how these components fit together in the case. The servo has not yet been installed.
Step 4: Install Planet Carrier One-Way Clutch
The one-way clutch fits into the planet carrier. The carrier and one-way clutch should be lubed with transmission assembly lube and checked for proper operation. Check the one-way clutch rollers and cage for integrity. The one-way clutch should be replaced in the interest of durability.
Step 5: Fit Steel Center Support
Seat the stamped-steel center support in the planet carrier and check for smooth operation against the one-way clutch. It should turn one way but not the other and do so smoothly.
Step 6: Install Center Support
Install the center support and planet carrier. Seat them into the ring gear and direct clutch. The direct clutch can be seen here, in the middle below the planet gears.
Step 7: Seat Direct Clutch
The planet carrier can be seated into the ring gear and direct clutch with a little twisting of the small input shaft, which is splined into the direct clutch.
Step 8: Install Spring Tabs
The anti-clunk spring tabs must face outward to do their job properly. These springs stabilize the center support and prevent “clunking.”
Step 9: Secure Center Support
Secure the center support with a large snap ring, which has been installed. Between the snap ring and anti-clunk springs, the center support should be secure.
Intermediate Internal Assembly
Step 1: Install Sun Gear and Thrust Bearings
Fit the sun gear into the planet gears, which can be tricky. With the sun gear comes the number-5 thrust bearing, which is located on the sun gear head. The number-5 thrust bearing goes between the sun gear and drive shell (which you install next). Coat the gear teeth and bearing with assembly lube and work the sun gear back and forth. This should seat the sun gear firmly.
Step 2: Install Drive Shell
The drive shell fits into the planet carrier right after the sun gear and rides the number-5 thrust bearing.
Step 3: Install Number-4 Thrust Bearing
Inside the drive shell is this number-4 thrust bearing, which buffers against the reverse clutch and one-way clutch assembly. Generous lubrication is best with each of these assemblies.
Step 4: Fit Forward Clutch Hub into Drive Shell
This is the forward clutch hub, which is seated in the drive shell. It receives the number-3 thrust bearing (shown). The reverse and forward clutches ride against this bearing. The reverse clutch frictions spline into this hub.
Step 5: Install Reverse and Forward Clutches
Spline the reverse and forward clutch assemblies into the drive shell and clutch hub. You will likely have to rock these assemblies back and forth to get them to seat. This is the way your AOD should look once you seat the reverse clutch.
Step 6: Install Overdrive Band
The overdrive band installs wet with transmission fluid and seats against the anchor pin. The servo places pressure against this band, locking the reverse clutch. Some people incorrectly call this the overdrive drum. It is the reverse clutch, which houses the reverse clutches and splines into the forward clutch and input shaft.
Intermediate Clutch Installation
Step 1: Install Intermediate Clutches
Place the intermediate clutch discs and steel plates in the case. These clutches lock the reverse clutch drum. They should also be soaked in transmission fluid prior to installation.
Alternately lay the clutches and plates until the last steel. You check the intermediate clutch clearances differently from the rest, with a depth micrometer instead of a thickness gauge (a depth micrometer can be found at nearly any tool supply house). The clutch stack depth from the leading edge of the case (where the pump seats) to the first steel should be 1.634 to 1.636 inches for all V-8s and 1.629 to 1.640 inches for all V-6s. Check this depth in two locations 180 degrees apart. Clutch steels are available in four thicknesses.
Step 2: Check Intermediate Clutch Depth (Precision Measurement)
When you get to the last intermediate steel plate, check clearances with a depth micrometer. Position the depth micrometer at the pump to the transmission face and take the measurement from there to the clutch plate.
Front Pump Assembly Installation
Step1: Install Front Pump Thrust Washer
The nylon thrust washer sets up clearance between the pump and reverse clutch assembly. Clearance should be .030 to 056 inch for V-6s and .040 to .075 inch for V-8s.
Step 2: Install Pump Gasket
Lay a thin film of transmission assembly lube on the pump gasket and transmission mating surface. Make sure all passages are properly lined up. Aslo check the pump passages for proper alignment.
Step3: Install Front Pump
Carefully position the front pump and love-tap it into place with a mallet. Confirm the bolt-hole alignment by hand-threading bolts and carefully run the bolts down. Torque bolts in a crisscross pattern to 16 to 20 ft-lbs.
Step 4: Install Secondary Input Shaft
Insert the secondary input shaft and splined into the direct clutch, which cannot be seen, but is felt when the shaft is seated. The secondary input shaft joins the geartrain when you are in overdrive/lockup.
AOD factory evolution includes larger servos to increase durability. Early on, the AOD was fitted with the “C” overdrive servo, which is the smallest. Beginning in 1985, Ford enlarged the overdrive servo (known as the “B” servo), which increased apply force by 30 percent, according to Ford. The “B” servo includes the piston (PN E0AZ-7F200-B) and the cover (PN E0AZ-7D027-D). The best overdrive servo, which is being used in this application, is the “A” servo with the piston (PN E9SZ-7F200-A) and the cover (PN E9SZ-7D027-A). The “A” overdrive piston increases band holding power by nearly 50 percent and without any transmission modifications.
Band and Servo Installation
Step 1: Align Bands for Servos
Manipulate the geartrain and bands so the servos and band actuating rods line up. The bands should be seated against the anchor pins at this point.
Step 2: Install Low-Reverse Servo
Install the low-reverse servo, ensuring the piston and bore are liberally lubricated with transmission assembly lube. Make sure the actuating rod is firmly seated in the band.
Step 3: Install Low-Reverse Servo Cover
Use a snap ring to install the low-reverse servo cover. Apply pressure on the cover and seat the snap ring. Because snap rings can pop out, make sure it is firmly seated.
Step 4: Install Overdrive Band Servo
Give the overdrive band servo cover and its seals plenty of lubrication. Make sure the seals are free of distortion and sit squarely in the grooves. It is generally a good idea to wash the seals before lubricating them.
Step 5: Install Overdrive Servo Piston
Lube the overdrive band servo piston before installation. Again, pay close attention to seal integrity. Any distortion will cause servo malfunction.
Step 6: Install Servo Piston Return Spring
This is the 1989 level E9SP “A” overdrive servo, which offers the broadest surface area and greatest holding power.
Step 7: Install Overdrive Piston and Cover
Note the generous lubrication used here. You can never have too much. Pay very close attention to the seals as you press the piston into the bore. They’re easily distorted and damaged.
Step 8: Seat Servo and Cover
Seat the piston and cover gingerly with a hammer handle and snap ring installed. Make sure the servo actuating rod is seated in the overdrive band.
Step 9: Match Piston Rod and Band
This is what proper actuating rod and band installation looks like. The rod should be seated in the band as shown.
The throttle valve does the work of two components: the vacuum modulator and the kickdown linkage. The vacuum modulator in earlier Ford automatics regulates control pressure based on load and throttle position.
The throttle valve’s function is quite simple. Based on throttle position and cable/rod tension, the throttle valve handles control pressure to all servos and clutches. When you go to wide-open throttle (WOT), you want high-control pressure for a firm upshift. The firm upshift comes from solid clutch and band engagement.
By the same token, low cable/rod tension softens the upshift because line pressure is lower and slippage is more apparent. What you want from the TV cable or rod adjustment is a later, firmer upshift without being too firm. Ford strongly suggests using a line pressure gauge for TV cable or rod adjustment. This is an adjustment that must be precise or it can cause serious transmission damage.
AOD applications fitted with central fuel injection or a carburetor employ a throttle valve rod instead of a cable, which calls for a different type of adjustment on a spring-loaded control rod and pivot at the transmission. There’s also an adjustment at the throttle body or carburetor. In applications with TV cables, adjustment is at one location at the throttle body. Cable tension is controlled at the throttle body (see Chapter 9).
Regardless of whether you have a TV cable or rod, adjustment boils down to how and when the transmission shifts during normal driving and WOT. During normal acceleration, you want a firm (but not hard) shift. At WOT you want a hard upshift when the engine reaches its torque peak for best results. During deceleration, downshifting automatically is normal and you should never feel it. If you can, control pressure is too high. Line pressure should
Aftermarket service and valve body kits for the AOD contribute to improved shift quality and transmission life. These kits are available separately and they’re also included in overhaul kits. TCI Automotive transmission overhaul kits, for example, include just about everything you need to rebuild an AOD, including all soft parts such as gaskets and seals, friction discs and steel clutches, low-reverse and overdrive bands, filter, and servo pistons. And when you build, you want to choose a torque converter from one of many manufacturers such as B&M, LenTech, TCI Automotive, TransGo, Bowler, and others, based on how you intend to use your AOD.
Accumulator and Valve Body Installation
Step 1: Install 2-3 Accumulator Piston
Lube the 2-3 shift accumulator piston and seat it in the bore. This installation varies from generation to generation as there were run ning production changes. The 2-3 shift accumulator was finally perfected by the 1989 model year and is available from a variety of transmission parts suppliers.
Step 2: Install Accumulator Return Spring
Next, install the 2-3 shift accumulator return springs. Some applications have two springs; others have one. The best example to go by is the transmission you have and the model year unit you’re working with.
Step 3: Lay Down Valve Body Gasket
Place the valve body gasket. Make sure all surfaces are hospital clean. Even the smallest speck of dust can cause leakage and pressure loss. You can use a thin film of transmission assembly lube for gasket security.
Step 4: Install Valve Body
This valve body has been rebuilt and fitted with a TCI Automotive shift kit for firm shifts and less wear and tear. Valve body installation mandates the utmost care with proper bolt placement.
Step 5: Check Manual and Throttle Valve Alignment
The manual and throttle valves should be checked for proper operation. The manual valve has detents to keep it in the selected gear range. The throttle valve is linear and spring loaded. Make sure both valves operate smoothly without sticking.
Do an operation check of these valves using compressed air.
Step 6: Torque Valve Body Bolts
Torque the valve body bolts to 80 to 100 in-lbs beginning with light hand tightening to seat the valve body, then torquing in one-third increments.
Step 1: Air Check Servos and Clutches
Check the servos and clutches with air via the output shaft’s governor passages. When air is applied, listen for servo and clutch piston movement.
Step 2: Rebuild Governor
Disassemble, clean, and inspect the governor, which is mounted on the output shaft. From left to right are the end plug, sleeve, spring, governor valve, governor main body, cover with two bolts, and counterweight attachment screws. (Not shown here is the counterweight.) A small filtering screen should always be included. Some transmissions are missing this screen due to previous rebuilds. The screen can be cleaned or replaced. Most transmission parts supply houses have them.
Step 3: Inspect Governor (Critical Inspection)
The governor spins on the output shaft, affecting line pressure as vehicle speed changes. Shake the governor back and forth to ascertain valve freedom and movement.
Step 4: Install Governor Assembly
The governor slides onto the output shaft. The ball acts as a drive key, much like a square key in a keyway. If the ball is missing, the governor does not function properly.
Step 5: Secure Governor with Snap Ring
The snap ring keeps the governor in place on the output shaft. Make sure the snap ring is deeply seated and secure.
Step 6: Install Tailshaft Housing Gasket
Install the tailshaft housing gasket using a thin film of assembly lube for adhesion and sealing. The tailshaft housing is also known as the extension housing.
Step 7: Tighten Housing Bolts
Install and secure the extension housing. The bolts should be torqued to 16 to 20 ft-lbs in a crisscross fashion.
Step 8: Choose Pan and Gasket
The transmission pan goes on next, using the best gasket available. Use a composite silicone/steel combination originally used by Ford, which seals like no other gasket.
Step 9: Install Pan
Torque the bolts to 6 to 10 ft-lbs. Avoid using a cork or cork/rubber gasket because they leak.
The automotive performance transmission aftermarket enjoys a wealth of options for building an AOD or AODE/4R70W. Most AOD performance parts are little more than off-the-shelf Ford pieces that were factory upgrades made over the production life of both the AOD and AODE/4R70W transmissions. The entire AODE/4R70W geartrain can be swapped into the AOD with great results, which takes the confusion out of improving the AOD. Dynax frictions, which have a proven track record are a great choice for an AOD build. As mentioned previously, the wider 2-inch overdrive band and reverse clutch drum improve durability. The wide-ratio 4R70W gearset improves acceleration with a 2.84:1 first gear winding out to a .70 over-drive ratio. If you have the budget, the aftermarket has your 4R70W performance parts.
Baumann Electronic Controls offers a wide variety of performance parts and control systems for the AOD. The ReCalPro Valve Body Recalibration Kit raises full-throttle shift-points about 1,100 rpm. It is all about fine-tuning the pressure control system where you get both performance and durability.
Once you get the hydraulic control system where it needs to be for improved performance and durability, you want solid mechanicals to back it up. One AOD weakness is the direct clutch. It can be remedied by the Alto Direct Clutch Pack Kit, which allows you to increase the number of clutches to seven or eight. You have a choice of the AOD’s cast-iron direct clutch drum or the stamped steel, which is lighter.
The Sonnax Pressure Regulator Boost Valve, available from a variety of aftermarket transmission performance suppliers, is another path to performance and durability because it solves pressure regulation issues that have long plagued the AOD. This kit consists of the booster valve and a sleeve that eliminates the sticking pressure regulator boost valve problem and resulting failure.
You should stay with a stock Ford transmission pan because they are of the best quality. They also fit best and don’t leak. Another solution is a Ford Bronco AOD pan, which is deeper and has greater capacity. If you want more fluid capacity and better cooling, go with a finned cast-aluminum pan. This type gets rid of heat best, thanks to its cooling fins and the heat transfer advantages of cast aluminum.
Keep a close eye on casting porosity with cast aluminum, which can cause leakage. Casting porosity is a fundamental weakness in aluminum and iron castings where excessive amounts of air get into the molten mixture before it cools and cures. The casting becomes more like a sponge, allowing fluid to leak through the casting and onto your garage floor. You can coat the inside of the cast pan with GE Glyptal, which is an excellent sealer. The key to success with Glyptal is good paint adhesion, which means you must have a clean surface before application. If the pan already had transmission fluid in it, do not use Glyptal.
As you assemble your AOD transmission, be aware of torque specifications and follow them to the letter. Incorrect torque can do permanent damage, especially to lightweight aluminum castings that depend on precise tension and bolt stretch. When you are assembling clutch packs, check clutch plate clearances and follow specifications to the letter. During final assembly, always check endplay.
Written by George Reid and Posted with Permission of CarTechBooks