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Automatic Overdrive Transmission Swap
An Overdrive Transmission in an Early Car Gives Balanced Performance for Acceleration as Well as Quiet and Economical Highway Performance
February, 2009
By Wayne Cook
Photography by Wayne Cook
 |  Here&8217s the AOD four-speed...  Here’s the AOD four-speed automatic overdrive transmission ready to go into our &821765 coupe. Windsor-Fox can furnish a transmission for your project, or you may wish to supply your own unit. |  All three of these AOD conversion...  All three of these AOD conversion parts are custom fabricated at Windsor-Fox. At the top is the shift rod, which allows the use of the stock floor shifter. It&8217s adjustable for exact operation, and allows the detents on the factory 1965-66 shifter to work perfectly with the four-speed automatic. The old "snow drive" position where the car would start out in Second gear becomes the Overdrive position. Below the shift rod is the special crossmember that allows the AOD to be bolted into the early car. Windsor-Fox has crossmembers available for many early Ford conversions, both for the AOD and the T5. At the bottom is the parking-brake actuation lever. Used in conjunction with the crossmember, it allows the parking brake to be retained and operated in the stock manner. |  Windsor-Fox now offers this...  Windsor-Fox now offers this complete AOD control cable kit. Made at Windsor-Fox especially for this application, the cable kit allows for exact control of the important relationship between the throttle position and the AOD&8217s control lever on the side of the transmission. This kit must be with carbureted engines. On an EFI/AOD conversion, a 5.0 Mustang control cable can be used. |  Also required for the swap...  Also required for the swap is the block plate, transmission dipstick and tube, and neutral safety/backup light harness. |  The transmission mount is...  The transmission mount is a C4 unit. Don’t make the mistake of ordering an AOD mount because it won&8217t work for this application. A new mount is strongly recommended. |  One important aspect of the...  One important aspect of the AOD conversion is use of the correct flexplate. There must be no mistakes here, and for our job there are two factors we are concerned with. Early and late engines have a different balance weight. Early engines like the 289 have a 28-ounce balance weight, while later engines like the 5.0 require a 50-ounce weight. The second factor is the diameter of the flexplate. The late-model AOD transmission requires a larger-diameter flexplate than the early C4. Since we’re mating an early balance 289 with a late-model-diameter flexplate transmission, we need both characteristics in one part. This photo shows the 289 flexplate that came out of our car at the left. It has the right weight but the wrong diameter. At the right is an AOD flexplate, which has the correct diameter but wrong balance weight. Neither of these flexplates will work for our swap, something we want to highlight so you won&8217t make a mistake. |  These two flexplates are both...  These two flexplates are both large-diameter units. We’ve set the balance weights side by side so you can see the difference. For our application, we’ll use the flexplate on the left with the correct diameter and the smaller 28-ounce balance weight. These late-model-diameter flexplates with the early model balance are available at Windsor-Fox. If you’re inclined to scour the boneyards, look for a unit from a 1969 351, but they&8217re getting scarce. |  Although we&8217re talking...  Although we’re talking about a 1965 Mustang in our story, the information here pertains to overdrive conversions for many early Fords. If you&8217re doing an AOD conversion into an early Falcon or Ranchero, this nifty lever and bellcrank arrangement will allow you to keep your stock column shifter. |  Here we see the C4 three-speed...  Here we see the C4 three-speed on its own out of the car. You’ll need to support the engine while the transmission is out of the car. We’re using a screw jack, but you can use a piece of lumber between the engine and firewall, or a floor jack if you&8217re doing the job on jackstands. |  We&8217re moving right along...  We’re moving right along here as we&8217ve already installed our block plate. The flexplate is in position on the crankshaft and is now being torqued down to specifications, 75-85 lb-ft for all engines per the 1966 Ford Shop Manual. |  Be sure to fill the new torque...  Be sure to fill the new torque converter with at least one, and preferably two, quarts of the correct-type Mercon fluid. If you forget to do this, you’ll have to take the whole job apart because the transmission won&8217t pump up. |  The next step is to install...  The next step is to install the torque converter onto the transmission. The converter must go past two steps, or detents, in order to seat properly. When the transmission is installed against the engine, there should be a small amount of play available between the converter and flexplate. You should be able to move the converter up and back this short distance. If the converter is up against the flexplate with no play available, the installation is incorrect. You must remove the transmission and correct the problem. |  It&8217s time to install...  It’s time to install the AOD transmission into the vintage Mustang. You&8217ll definitely need some type of jack, as the transmission is far too heavy to manhandle safely, even with two people. Also, it takes time to make your connections once the unit is in position. |  With the transmission in the...  With the transmission in the correct position, we begin making our connections. Here, the bellhousing bolts go into place. |  This mockup shows how the...  This mockup shows how the control cable attaches at the carburetor. The special bracket that retains the cable housing in the correct position is a Windsor-Fox item. The cable attaches to the primary throttle shaft in this example. Sometimes the cable end attaches to the carb throttle bracket next to the accelerator linkage on the driver’s side of the engine. The location varies according to specific equipment. On our car, the cable travels around the front of the engine in a gentle curve on its way to the driver&8217s side of the transmission. |  No detail is overlooked at...  No detail is overlooked at Windsor-Fox. Here we see a heat-resistant sleeve installed over the control-cable housing to protect the housing as it travels near the exhaust system. |  Down at the transmission,...  Down at the transmission, the boss on the side of the transmission case is positioned perfectly to receive the cable kit mounting bracket. The lever is furnished with the cable control kit, and is installed in the upright position as shown. Smooth travel of the cable within its housing, with no binding, is imperative. Make any needed adjustments toward that end. Between the return spring at the carburetor and the spring shown on the transmission end of the casing, our control lever always returns to bottom as the throttle is released. |  The AOD transmission is 1...  The AOD transmission is 1 inch longer than the C4, so the driveshaft must be shortened by the same amount. This is a good opportunity to replace those worn U-joints. In this photo, Ed installs the newly shortened driveshaft into our car. |  Here&8217s the finished installation....  Here’s the finished installation. Notice how nicely the Windsor-Fox crossmember completes the job. The parking-brake setup works perfectly, and the crossmember allows for transmission pan removal without removing the crossmember. We can’t wait to get this car out where there’s some open space. Those semis won’t be blowing us into the weeds anymore! |
We've said it numerous times--nothing beats an overdrive transmission in an early car for balanced performance. Even with the lower rearend gears many of us run for acceleration, quiet and economical highway performance is possible. Keeping the pace with modern cars while also enjoying enhanced fuel economy, better high-speed performance, and quieter operation is easy. In a vintage Mustang, a T5 manual transmission or AOD automatic overdrive transmission is extremely worthwhile and a relatively easy swap. Few things top the feeling when you're out on the highway and the tach drops from three grand to two grand as the car quietly slips into Overdrive. We have a good friend with a pale yellow 1965 coupe with an A-code 289 and C4 automatic. With a fresh engine rebuild, he wanted to maximize engine life and gain improved high-speed performance as well, so he decided to make the swap to an AOD. It’s gotten to the point where it’s nearly a bolt-in proposition thanks to parts offered by the EFI and overdrive conversion specialists at Windsor-Fox Performance Engineering. Trust us--it’s one of the greatest things you can do to enhance the driveability and fun factor in a vintage Mustang.
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