Modifying

AOD Automatic Transmission

For All 1983-88 Cougars / Thunderbirds

Page Revised: 10 May 2019

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Article by
Eric Dess

The Ford AOD transmission from the 1980s isn't known to be the strongest transmission. It was used in a wide variety of rear-drive Ford passenger cars and trucks throughout the decade, but it really never seemed to get better as time went on. The only exception seemed to be the heavily-strengthened internals for the 1989-93 Thunderbird Super Coupe and 1989-90 Cougar XR-7. The rest of Ford's lineup got the "regular" version. Eventually the AOD was replaced with an electronically-controlled version with modified internals. So our AOD was really the last of its kind: all mechanical and hydraulic, no sensors, no electronics.

It's not like the AOD is a rare thing...quite the contrary. There were millions of them installed in Ford vehicles for 15+ years, and you can still find them in salvage yards today. So parts are still plentiful and so are your options should you choose to beef one up.

Some of the details here are the same as what's in the Transmission Help section, but we wanted to break out a dedicated page to the AOD to assist with modifying it for your purposes.



Transmission Cooler
External Transmission Cooler

Adding an external transmission cooler will add greatly to the life of your AOD. If you tow, are in lots of stop-and-go traffic, do lots of highway driving, or idle quite a bit, then you likely need to get an additional cooler. Now from the factory, all automatics have a cooler that's built into the side of the radiator. It's a noble idea from the factory...in reality, though, it's just adequate enough to keep the transmission cool. The new external cooler will bypass the cooler in the radiator, and will actually attach to the front of the a/c condenser. You will need to either adapt your stock transmission lines, or cut them and attach new ends, in order to get them hooked up to the new cooler. Adapting is much simpler and only requires a few new brass fittings. The advantage is that you can always go back to the radiator tank cooler if you need to. You can buy transmission coolers from almost any parts store. You won't need anything really heavy duty; buy one for the minimum GVWR or the next one above that.


Shift Kit
Shift Kit

The ubiquitous shift kit will firm up your shifts, prolong the life of the transmission, and give you slightly better gas mileage. Shift kits work better in conjunction with a higher stall torque converter but that's not required. Most of these older-style mechanical transmissions (meaning those without the aid of electronics) can benefit from a shift kit. And you can tailor the kit to make the transmission shift to match your driving style—crisp, firm, or head-snapping. The trouble is, how do you know which kit to buy? In this area especially, you get what you pay for. Now we won't be slamming any companies' products here, but typically the lower-priced kits are going to give you more problems than the more expensive kits. The Baumann Engineering kit and the Trans-Go kit are both excellent and are highly recommended. If you decide to install the kit yourself, it's about a 4-hour process and can be tricky if you're not careful. When in doubt, have a professional do it for you.


Upgraded Internal Components

The most popular item to upgrade for the AOD is the Ford Racing wide ratio upgrade kit (M-7398-D), which is the same as those found in the 1989-93 Thunderbird Super Coupe. It's not cheap but it's a worthy upgrade.

Also, a single piece input shaft will provide greater strength than the stock two-piece unit. Again, it's expensive but is a lot stronger.


Valve Body and Modifications

An aftermarket recalibrated valve body greatly improves the strength and performance of your AOD. For around US $500 or so, you can get a professionally built valve body that makes your AOD shift way better than new. There are many companies that offer these, such as Silverfox Performance Transmission, Performance Automatic, LenTech Automatics, and many more. Be sure to do your homework on these, and also figure for having it installed if you're not willing to try it yourself, as this can be a pretty daunting job for the inexperienced.

There is also the "epoxy mod", where AOD owners won't have to fear about overdrive kicking in at wide open throttle. Third gear will be held so long as you hold the accelerator; letting off allows OD to kick in. It requires a drill bit and some epoxy; this is a free and time-tested mod that solves one of the annoying issues about a floor-shifted AOD transmission. More information can be found in this thread.


Torque Converter
Torque Converter

The stock AOD torque converter stalls at approximately 1500-1800 rpms. This is okay, but for engines with moderate to heavy modifications, a higher stall torque convertor is a must. Usual ranges vary from 2000 rpms to 3500+ but you'll need to talk to a transmission specialist to find out what stall speed is best for your car, as you need to select a converter to match the camshaft you're using. Remember that when you raise the level of camshaft performance with the motor, you will almost always need to raise the converter to match.



Rebuilding/Replacing An AOD Transmission

See the Transmission Help section for more information.