Automatic Transmission Help

For All 1983-88 Cougars / Thunderbirds

Page Revised: 10 May 2019


Article by
Eric Dess

If you are experiencing trouble with your Cougar's automatic transmission, believe us, we've felt that pain many times before. Or perhaps you would just like to prevent that from happening in the first place. This section is definitely for you. Remember, although these are tried-and-true experiences, second opinions never hurt.

Taking Care of Your Transmission (C3, C5, AOD)

Fluid Change

It is recommended in your owner's manual that all automatic transmissions should have the filter and fluid changed at least every 30,000 miles if not sooner. This is a pretty good regimen to follow. Usually a trans fluid/filter change is fairly inexpensive at a shop, and less if you do it yourself. However, there are two schools of thought here: 1) routine maintenance is good, or 2) if it ain't broke, don't fix it.

In talking with several professionals, including our own personal mechanics, the thought of keeping the fluid as-is for extended periods of time is not an uncommon sentiment. The theory is that the fluid will contain deposits that can build up in the passages throughout the valve body. These deposits are akin to carbon buildup in the upper intake plenum. The transmission "gets used" to having these buildups, which are normal. If you change the old fluid, the new fluid will flush away those deposits, and the likelihood of changing the transmission shifting and wear patterns is high.

Does this mean you shouldn't change the fluid and filter? Well, not if you can help it. So long as the transmission is shifting well and you suspect no ill behavior, you'll probably be alright. But there will come a point where you will need to change the filter at the very least. If you suddenly can't put the car in gear, if the shifting becomes erratic, if you have hesitation, or sometimes if the car won't even start, those should be clues that you may need a transmission filter change. And obviously, when you take the transmission pan off, you're going to lose all the old fluid. So when you put the new fluid in, you may want to put some transmission fluid additive in with it. It's supposed to keep all those deposits in place, so that your transmission should shift about the same as with the old fluid. We recommend the additive simply because it's inexpensive insurance. Any good parts store will have trans fluid additive.

In addition, all factory automatic transmissions used in our cars can benefit by using synthetic transmission fluid. Because of the man-made components in the fluid, the passageways inside the valve body will become slipperier, thereby allowing better fluid passage and reducing friction (and heat). Remember that heat is the number one killer of transmissions; anything you can do to keep the heat out of the transmission will keep the inevitable rebuild away.

Transmission Cooler
External Transmission Cooler

Adding an external transmission cooler will add greatly to the life of your gearbox. 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 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.

By the way, the 4-cylinder automatic transmissions (C3 or A4LD), used in rear-drive 4-cylinder Ford applications (including the Mustang and Ranger), are usually weaker pieces to begin with since they weren't designed to handle the torque of a V8. Any shift kits or souping up in these would probably hasten transmission failure.

Torque Converter
Torque Converter

The stock 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.

Precautions (AOD only)

Since all V8 Cougars and all 1987-88 models had the AOD (along with optioned 1986 3.8L V6 cars), it's safe to say it was one of the most commonly used transmissions in the 1983-88 body style. But thanks to that AOD band it's also the most troublesome. AOD's have problems that are all their own and you will need to know about your transmission more than owners with a C3 or C5.

Brass Bushing Replacement Kit

The main thing to watch is the TV/kickdown cable grommet on the throttle body. This mainly concerns 1986-88 V8 models but is also true of 1988 V6 cars. From the factory the end of the TV cable is pushed into a plastic grommet on the underside of the throttle body lever. At the time of design it was probably a money-saving solution. But it's proven to be a faulty design, one that can kill an AOD in a heartbeat. What happens is that over time, and with constant heating and cooling, the plastic grommet can crack and allow the TV cable to become disconnected from the throttle body. Driving without the TV cable attached will almost immediately kill an AOD. Fortunately there is a very inexpensive cure for the problem—Ford has issued a kit (p/n F3SZ-7H303-B) that completely replaces the grommet with a brass bushing and hairpin. We highly recommend that you buy and install this kit on your car. For the price, buy a spare and throw it in the glove box. You can also find these kits at some later model Mustang restoration companies.

Also, we recommend that you do not drive in OD all the time. This has been a debate in the Ford community for years, since even the owner's manual states that OD is your "normal" driving gear. However, with both professional recommendations and personal experience under the belt, we're very confident in telling AOD owners to bypass OD and head straight for D when driving in the city or under 45 mph. The premise behind OD is that it lets your engine spin at lower RPM's, reducing drag and increasing gas mileage. If you drive in town a lot and the car shifts constantly between OD and third gear, you're not saving gas, reducing drag, or saving the OD band—in fact, just the opposite occurs. This greatly weakens the OD band which is already a fairly weak piece to begin with. As a general rule, if you'll be driving under 45 MPH for under 10 minutes at a time, lock out OD and shift into D. The OD gear should only be used for highway use, or extended driving over 45 MPH.

Drive without the kickdown (TV) cable attached. You will cause immediate and severe damage to the transmission.
Pretend it's a 5-speed by manually shifting gears under hard acceleration. Column shifters especially. This shortens the transmission's life, and it's too easy to miss a gear. If you need to downshift when going down a hill, or upshift from a stop on slippery surfaces, that's okay.

Warning Signs (C3, C5, AOD)

Unfortunately, Ford transmissions from our era usually don't give a whole lot of warning signs before they go. In fact, they usually just go all of a sudden. If you notice that the car is not shifting into gear right away, or won't upshift or downshift into a certain gear, that's usually a good sign that there's something amiss inside the transmission. Or, if you hear clunking coming from the transmission area, that's another omenous sign. In general, anything other than normal shifting is not good and should be taken care of immediately. In a lot of cases it's just a simple matter of changing the filter and fluid; a new filter sometimes works miracles. For C3 and C5 models, it could be something as easy as a modulator change. But for those instances where it doesn't make any difference, you may be looking at a transmission rebuild.

Rebuilding/Replacing A Transmission (C3, C5, AOD)

Sooner or later your transmission is going to need rebuilt. Since nothing man-made lasts forever, it's simply a fact of life that you must deal with. The unfortunate reality is that an automatic transmission rebuild from a professional trans repair shop is not cheap—plan on spending a minimum of $500, and a lot of rebuilds can go upwards of $1000. There is usually a full day's work inside a single transmission, as there are many small parts (springs, check balls, etc.) that must be placed in their proper order. If you've ever seen the inside of a transmission all torn apart, you'd understand—it's a mess in there. The actual cost of rebuild components is usually way less than the labor costs involved. Plus, since the C3, C5 and AOD are all from the same metric family of Ford transmissions, the costs are usually higher than a standard ("American") transmission. Essentially what you're paying for is the expertise and time of the professionals rebuilding your transmission.

So what happens if you cannot afford a rebuild? Or say your transmission has been rebuilt once and it goes out again—what to do now? As with most things that are older, eventually you're going to need to replace the transmission. Sometimes the cost of replacing vs. cost of rebuild will have the most profound influence on your decision. But finding the right transmission can be a challenge. Here's a chart that can help you make an informed decision, with pros and cons for each.

Salvage yard Relatively inexpensive. Can inspect before buying. Exact replacement in most cases. Decent selection. Replacement transmission could also be bad—you won't know until it's in. Labor involved in installing (although sometimes yards will offer to install). Must return core. Limited warranty (sometimes as little as 30 days) means you must install quickly.
Transmission shop pre-rebuilt Uses cored-in transmission for a rebuild—very cost-effective. Usually comes with warranty. Can install if needed, but you can buy outright. Quality of rebuild components may vary. Built-in profit means this can be expensive if you don't shop around. Must leave or return a core.
Race rebuilt transmission All the best components. Pre-tested—all the bugs worked out. Cost can rival a professional rebuild. Decent warranty. Expensive shipping charges. Labor involved in installing. Not intended for your average daily driver.

You will have to weigh all factors and make the best decision for yourself. For example, if you use your Cougar for daily driving only, you'll want to look at a salvage yard or transmission shop rebuilt transmission. But if you're hopping up your motor and need something beefier, but you don't necessarily want to rebuild, it's going to be more cost-effective in most cases to buy a professionally-built race transmission.

Before you do anything, though, please talk to a transmission specialist before you start the rebuild, as they may have access to similar parts at decent prices. Remember to shop around and get several estimates before making your decision. Ultimately you are in control of what happens to your transmission. Be sure you know what you're getting into before you shell out any money!

Transmission Specialty Companies