Probably one of the
most popular transmission exchanges that are being performed on '60s and '70s Ford cars and trucks involves using the Ford AOD or automatic overdrive. The AOD was used originally on '80s and early-'90s Ford, Lincoln and Mercury products and in the F-series pickups and E-series vans as well. The AOD can be a relatively easy transmission to transplant and the additional 4th-gear overdrive can give you added fuel savings, especially in cars and trucks using taller rear axle ratios. Because Ford used these transmissions in so many production vehicles, the Ford AOD is relatively easy to locate at a used parts yard and can be purchased for a reasonable price. The Ford AOD does not need a computer to function properly either. The throttle valve function is mechanically activated and the torque converter lock-up function was contained entirely within the transmission case. Ford later used this transmission as a basis for their newer overdrive transmissions, the electronic overdriven AOD-E, which was used beginning in 1993 and in the 4R70W which was used on '99 and up production cars and trucks. Using an AOD transmission will effectively lower a 3.73:1 rear axle ratio down to a fuel-saving 2.49:1.
The AOD transmission can be identified in several ways. Its prominent 14-bolt pan is probably the easiest way. The pan is basically square but the back two corners are tucked in a little tighter than the front corners making the pan look like home plate with the front point cut off. Many of the original pans also have Automatic Overdrive and Metric and the Ford oval logo stamped into them. The metric is sort of a misnomer because the internal parts are mainly metric, but not the hardware to install the transmission. Another way to identify the transmission is by the driver's door tag. Ford lists their transmission codes on their Vehicle Certification Label and these are a single letter located along the bottom of the label under the abbreviation TR or TRANS. The AOD transmissions will carry a "T" designation for any rear-wheel drive vehicles. Lastly, you can also check the tag attached to the transmission itself. This is located on the driver's side on the lower bolt that attaches the tailshaft to the transmission body. This tag contains many numbers; however, the first three-letter code on the top of the tag will say PKA (later AOD-E units with electric overdrives are designated as PKC). The AOD used two tail-shaft lengths; a shorter one for passenger cars had an E0AP casting, and the shorter truck castings read F2TP. The longer tail shafts had an E0LP casting on the passenger cars and an E0TP on pickups.
Automatic overdrive transmissions had replaced all C-4 and C-5 applications by the 1986 model year. The AOD has the neutral safety switch mounted above the valve body on the driver's side of the transmission and the speedometer drive cable is attached to the vehicle speed sensor on the driver's side as well. This transmission uses a throttle valve linkage or cable assembly to regulate the shifts. The AOD weighs 150 pounds, about 40 lbs. heavier than a C-4 or C-6 transmission.
Shift ratios are: 1st, 2.40:1; 2nd, 1.47:1; 3rd, 1.00:1; OD, 0.067:1; Reverse, 2.00:1.
These ratios are very close to the 2.46:1 ratio used in the three-speed C-4 and C-6 transmissions, but with the added benefit of an overdrive.
Some SVO-tuned Mustangs and some 1992 and '93 trucks came with a wide-range AOD, which had these ratios:
1st, 2.84:1; 2nd, 1.55:1; 3rd, 1.00:1; OD, .067:1; Reverse, 2.00:1.
Although the wide-range AOD is very popular with enthusiasts it can be very difficult to locate; however, you can purchase aftermarket rebuilding parts that will adapt a standard-ratio transmission to the wide-ratio configuration.
You will find a Ford AOD in these donor vehicles:
1980-'92 Ford and Mercury full-size cars with V-6 and V-8 engines
1980-'92 Grand Marquis and Crown Victoria with 4.6 or 5.0 V-8 engines
1983-'86 Ford LTD with a six-cylinder
1984-'93 Mustang and Cougar with transmission code PKA (V-6 and V-8)
1984-'86 Mercury Capri with transmission code PKA
1980-'92 Thunderbird with transmission code PKA
1985-'90 Bronco with 5.0 V-8 engines
1981-'93 Ford pickup and E-vans with V-8 engines
1991-'93 Ford pickups and vans with a 7.3-liter diesel engine
1980-'93 Lincoln (except Versailles) with V-8 engines
In terms of strength and reliability, you want to first find a unit out of a V-8 truck, then a V-8 car, and then a V-6 truck. The V-6 car transmissions are the lightest duty of the bunch. Truck and V-8 car transmissions have the slightly longer tail shaft as well. Also, the 1988 and up units featured better main-shaft lubrication than earlier units. Of course you want to look for pre-1986 transmissions for carbureted vehicles, to have the proper linkage necessary for those cars. Units for 1987 and up were for fuel-injected cars and will have the TV cable activation.
Once an AOD transmission-equipped donor car has been located it is a good idea to make a list of related parts that you'll want to remove from the car for use later. Besides the transmission, you want to get the torque converter, flexplate, and engine-separator plate. Be sure the kickdown lever and rod or cable comes with the transmission because these are disconnected during disassembly and you will be hunting around for them later when installation begins. Carbureted vehicles used a linkage rod setup for the throttle valve while fuel-injected vehicles used a TV cable system. Your existing shifter can be adapted to the overdrive configuration, but you might want to grab the comparable shifter out of the donor car too, at least get the correct shift indicator dial out of it. The driveshaft would be a good idea as well, because although you can normally use your existing driveshaft from a C-4, you at least need the shorter AOD slip yoke from it. A complete used driveshaft can be cheaper than purchasing a new slip yoke and will give you an extra driveshaft to be cut if necessary. No adapter U-joints are necessary to install the yoke on your existing driveshaft; both transmissions use the same Cleveland-type joint. Also, try to get at least the transmission end of the neutral switch harness. We recommend that the donor transmission be carefully checked before installation and the fluid and pan filter be changed. Some enthusiast Web sites have suggested using a V-6 torque converter in a V-8 transmission in order to get a slightly higher stall speed, but a good aftermarket converter with a higher stall is not all that expensive and would be the better way to go. The AOD harness contains four wires and controls both the neutral switch and backup lamps. The bellhousing mounting bolts are also important because the C-4 bolts are not long enough and standard replacement bolts do not have a long enough thread to be usable.
On cars using a Holley or Edelbrock replacement carburetor, a linkage corrector plate is available from those manufacturers to allow a TV linkage or cable assembly to be used.
The AOD is bolted to the engine by the use of an integral bellhousing. Because all 289, 302, 351W and 351C blocks used the same bellhousing bolt pattern, the AOD will bolt directly to earlier Fords using these engine sizes. Measure the distance between your two top mounting bolts on the bellhousing to be sure. They should be 5-1/8 in. apart. The 351M, 400 and 429 blocks have the same bolt pattern as the 460, (7-3/4 in. between the top bolts) so a big-block engine adapter would be required to install the AOD behind these engines. Installing the AOD in place of the earlier C-4 will involve moving the crossmember back about two inches and drilling new holes for the transmission mount so the crossmember does not interfere with the oil pan or the tailshaft mounting bolts. Some full-size passenger cars have a crossmember that has two sets of holes for the transmission mount. These crossmembers should line up without having to move them. Aftermarket crossmembers designed specifically for the AOD and Tremec transmissions are available from Mustang and Cougar suppliers as well. Because of a Ford engine balance design change in 1981, you should be searching for a transmission that has a mating flexplate available.
Selecting the correct flexplate to complete this conversion is important. The AOD was equipped with a 164-tooth flywheel with an 11-3/8-in. bolt circle and a 50 oz. balance weight. This is the same bolt circle and tooth count as the 1977-'81 C-4; however, the balance weight on the C-4 was only 28.2 oz. Newer 1982-'95 C-4 flexplates had the correct balance weight, but the tooth count was only 157 and the bolt circle was smaller at 10-1/2 in. So, when transplanting an AOD into a vehicle older than 1981, you must use the lighter balanced 1977-'82 C-4 flexplate with the AOD lock-up torque converter and also the 1977-'82 starter. You need to change starters because earlier 289 and 302 engines with the C-4 transmission used a 157-tooth flexplate and starter combination. Adapter flexplates are also available from aftermarket suppliers for both pre- and post-'81 balance weights. These can be as expensive as $200, but they are generally SFI-approved for racing applications.
If you are running headers, it may be necessary to bend the dipstick tube to clear the exhaust system. Properly cooling an AOD is critical to its life expectancy, so this might be a good time to consider piggybacking an additional transmission oil cooler or even using it to replace the existing radiator cooler altogether.
The throttle valve linkage or cable adjustment is very important to allow the AOD to shift properly. Start with a good bushing on your throttle linkage and check this bushing often after installation. Many complaints of improper shifting can be traced to this bushing. New bushings are less than $3 and can be obtained from your dealer or you can purchase aftermarket aluminum replacement bushings, which will last much longer.
To correctly adjust the TV cable assembly, release the locking tab on the TV cable and have someone hold the throttle full to the floor. Lock the tab down and mark this setting on the cable casing. This will be your maximum TV setting. Measure 5/16 in. back from that mark (with throttle still wide open) and scribe another mark as your minimum throttle valve setting. Then make a third mark halfway between both scribe marks (5/32 in. from either mark). Unlock the locking tab again and set the adjustment at this halfway mark to have a properly adjusted TV cable.
The driven speedometer gear for the AOD is the same as the C-4 and is clipped onto the end of the speedometer cable. The AOD drive gear is part of the output shaft and usually has seven teeth, although some have been found with eight depending on the original rear axle ratio of the donor car. Replacement Ford-driven gear part numbers have been added to our online technical database in the parts locator section of our Web site www.hemmings.com
. You may find you'll need different transmission fluid. Earlier Fords used type FA fluid, but the AOD requires 12 quarts of Mercon V fluid to fill the transmission and torque converter. The AOD does not have an oil pan drain plug; it is recommended that you install one while performing this exchange. Many suppliers offer two-piece add-on drain pan plugs.
Several aftermarket suppliers offer engine adapter plates that will allow you to install the AOD in earlier V-8 Fords including the FE blocks and Y-block series engines. Adapters are also available to attach an AOD to the Ford big-block engines and small-block Chevy engines too.
Checking around with some of our used parts sources, we found AOD transmissions easily available and for a reasonable price. We found used passenger car and truck units in the $300 to $600 price range. We also found some rebuilts for $550, but you must trade in a rebuildable unit. Driveshafts were located in the $85 to $150 range and used torque converters ranged from $60 to $100.
With some shopping, you should be able to find all the parts to complete this changeover for less than $1,200 and it should not take longer than a weekend to complete (with some prior preparation work). Installation of the transmission itself is probably the easiest part of this conversion. The modifying and attaching of the sundry cooling lines, linkages, cables and electrical harnesses will represent most of the time involved in completing it. Converting to an AOD transmission can be cost effective too, in terms of gas savings you should realize from the extra overdrive gear.
Some optional items you may want to purchase to complete the installation:
|AOD slip yoke-Spicer # 2-3-8341X||$56|
|U-joints-Spicer # 5-1200X (ea.)||$16|
|Lokar TV cable assembly||$65|
|Dipstick and tube assembly||$27|
|Neutral switch: Ford #D6RY-7A247B||$63|
|AOD Actuating Rod: Ford #E4AZ-7A232A||$19|
|OD column shift indicator insert||$20|
|Linkage corrector plate (Holley or Edelbrock)||$33|
This article originally appeared in the December, 2006 issue of Hemmings Muscle Machines.
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Ford 429/460 to Ford AOD
Adapter Kit Installation Instructions
1. Starter alignment plate
2. Bellhousing adapter plate
3. AOD converter spacer ring
4. Crankshaft pilot adapter
5. 1 ľ x 7/16 coarse flathead screws x 5
6. 1 inch 7/16 coarse flathead screw w/ modified head x 1
7. 3/8 sae flange nuts x 4
8. 7/16 sae torque converter bolts x 4
This kit allows you to bolt an AOD/AODE or 4R70W transmission to 429/460 series motors. In order to clear some of the bolt holes, we have rotated the transmission approximately 12 degrees clockwise. We recommend using a deep pan and 4x4 filter to keep the sump in the trans fluid during hard right turns. If you don’t want to use the deep pan, just overfill the trans slightly.
Because of the differences in the flywheels between years on the 429/460 motors, we developed the kit so you can continue to use your original flywheel. Prior to 1979 these motors were internally balanced. After that time they had a balance weight on the flywheel. Other types of small block Ford automatic transmissions can be made to work with this kit, but be aware that the spacing of the torque converter to the flywheel is different between the AOD/AODE/4R70W and other types of transmissions. Don’t use the converter spacer ring when using other types of transmissions, and watch the spacing carefully.
Make sure that your alignment dowel pins are present in your engine. Place the starter alignment plate and the bellhousing adapter plate onto your engine over the original dowel pins. Fasten the plates with the enclosed flathead screws to the block making sure that the screw with the modified head is in the lowest driver side location.
Attach the torque converter spacer ring onto your converter using the supplied flange nuts. Make sure the converter drain plug doesn’t interfere with the installation ( if there is one ). There is a relief cut into the spacer ring to accommodate a drain plug if there is one. Press the crankshaft pilot adapter into your crankshaft, making sure that it bottoms out in the crank. With the flywheel installed, fit the torque converter ( not in the transmission at this time )to the crankshaft making sure that with everything in place it can be pushed up to the flywheel with no interference. Now you can install the converter into the transmission ( make sure that it is spun into the transmission all the way ) and bolt the transmission to the engine. When the transmission is bolted to the engine, the converter must have some free play ( approximately 1/8 to 3 1/6 of an inch ). If there is no free play, don’t continue, find out why. The converter now bolts to the flywheel like a GM transmission with bolts instead of studs.
The starter needs to be from a late model small block Ford engine. These starters are also used in the V6’s. They are very common in the bone-yards. They also make mini high torque starters for the small block Fords.
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