5.0 Mustang & Super FordsHow To Drivetrain
Performance Automatic AODE - Hot Shift
Horse Sense: The AODE transmission has come stock in Ford Mustangs since 1994, and it is now called the 4R70 or 4R70W. The "W" stands for wide, as in wide gear pattern. These transmissions have the desirable low-gear set, which works best with the 4.6 modular engine, and they can be easily identified by the "W" stamped on the tailhousing.
When we last left off with our white '89 LX notchback ("Weekend Thrash," May '02, p. 208), we had begun the process of turning back the clock on an 80,000-plus-mile 5.0 Mustang. Our goal was to restore those aspects of the car most damaged by time and use. We did this by performing a tune-up and fuel-system rebuild, installing a full Bassani Xhaust stainless steel exhaust system, decreasing the parasitic drag on the engine to free up horsepower to the wheels, and upgrading the intake tract for easy breathing. Not covered in that story was the addition of an Unlimited Performance rear suspension (upper and lower rear control arms) and 3.73 gears, which really got things going.
What became obvious during our early ownership of the little coupe was that the AOD transmission, which was never intended for spirited driving in the first place, was in need of serious attention. After some blasts on the street and one day of dragstrip use, the transmission started slipping badly-to the point the car was no longer a pleasure to drive. We needed help. So we called our friends at Performance Automatic and Precision Industries-two aftermarket houses that know all about automatic-equipped performance cars-to get the inside scoop on what we'd need to fix our AOD blues.
Our first thought was to do a casual rebuild of the AOD, throw in a shift-improvement kit, maybe a wide gear pattern, and use a higher-stall converter to get the notch back in action. But Harvey Baker of Performance Automatic soon convinced us this was the old way of thinking. What he outlined for us was a jump to the next level in street automatic-transmission technology-the newly released Performance Automatic AODE transmission. The strengths of this transmission start from Ford Motor Company. The AODE is truly a state-of-the-art automatic transmission, with its pressure controlled internally, not coming from a TV cable as in the AOD. It's also much stronger from the start, able to hold 200 more horses in factory trim. And it has better internal components, including all gear material and hardware. Bottom line-it's an upgraded AOD ready for the next level.
In regard to the AODE, Harvey has become fond of saying, "We'd like to thank Ford for a job well done, but we'll take it from here!" Tom Cyr, owner and innovator at Performance Automatic, has developed a fully manual valvebody and transmission brake for the AODE. This brings the AODE into the performance market by mating a brute-strength transmission with the performance-car features of an Overdrive gear with electronic features (more on that later).
The unit we got for our car also included PA's large aluminum pan (12 quarts); Red Eagle race clutches; a Kevlar overdrive band; heavy-duty gaskets throughout; and a hardened, 31/44 shaft assembly. In testing, this bad boy has been taking more than 750 hp with nine-second elapsed-time potential. The best part is that even though this is an all-out race transmission inside, it also has the convenience of an electronically activated overdrive for full-on street use. As tested, our PA AODE transmission retails for $3,695.
Also working with the good folks at Precision Industries, we obtained one of the company's trick Stallion Series torque converters. These little gems can range in stall speeds from 2,400 to 6,000 rpm, and they have been tested in 1,600hp applications. Typically, a street car such as ours will see a two-tenths gain in the 60-foot times and more than a half-second reduction in elapsed time through the quarter-mile. These torque converters come with a two-year warranty, which includes a free stall adjustment in the first two years of ownership. That alone makes the converter a bargain, since you will likely change combinations on your car, making a converter change necessary. Ours is a 9.5-inch lockup converter with a 2,500-rpm stall. The lockup feature, which is activated electronically, mates the engine with the flywheel for 100-percent lockup, just as with a stick car. We found this feature alone was worth 10 horses at the wheels since the converter wasn't slipping and losing horsepower in high gear. As tested, our Precision Industries Stallion converter with lockup retails for $834.
There are points during the installation that you will have to fabricate a few items and be conformable with wiring. Mike Wilson, head technician at Paul's Automotive Engineering in Cincinnati, Ohio, easily handled our installation in one day. Of note, you will have to fabricate a transmission mount adapter. Mike did this out of a small piece of flat steel. This is done to offset the size difference of the AODE. We also had to remove one of the shifter linkage-mounting bosses so the stock AOD mechanism would mount up. For an additional tip, put a speed sensor in the correct location to avoid any transmission-fluid leaks. One sizeable problem is that if your car is like ours and is equipped with an X-pipe (ours was a beautiful Bassani), you will have to use an H-pipe to clear the PA transmission pan-it's that wide under the car. Begrudgingly, we bought a generic 211/42 inch H-pipe that easily cleared the new transmission.
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Once our transmission swap was completed, we took it outside to test. Full-throttle upshifts into Second gear happened instantly and were so firm that the basically stock 5.0 would spin the tires on street asphalt. Leaving on the tranny brake, First gear gave us little traction on the hard street tires we had mounted on the Pony rims. The Precision Industries converter was right where we wanted it. It allowed the engine to flash to 2,500 rpm and creep to 3,000 rpm if we held the engine on the brake for more than two or three seconds. Drive it like a normal car, with soft manual shifting, and the car was a dream to handle. Pull up to a stoplight and all you had to do was pull the shifter back into Low (for First gear). For Reverse gear, put the shifter in Reverse and hit the transmission brake. Part-throttle acceleration was similar to stock, since Precision Industries had done such a good job of choosing the right converter for us. We thought it might be a pain to drive such an advanced automatic transmission on the street, but this thing made the car fun again. No soft shifting, no stumbling as the stock torque converter held the car under 2,000 rpm, and no feeling that the transmission was chewing itself up while it accelerated the car.
Back at Paul's Automotive Engineering after out test drive, we strapped down our '89 coupe to the in-house chassis dyno to see what kind of horsepower was getting to the rear wheels. We hadn't done anything to change horsepower, but we had moved to a different dyno and changed gears (which has been shown to decrease rwhp). The best baseline pull was 188.1 rwhp, or right where we were after our initial round of bolt-ons. We were a little surprised since the original AOD transmission had been slipping so severely when we tested it at Kennedy's Automotive in Tonawanda, New York. But the changing of the converter, combined with the better transmission, was basically a wash.
We're not ones to race dynos, and we suggest you don't either. Comparing horsepower numbers when swapping transmissions and converters can be confusing and somewhat controversial. This is true because the rate of stall (with all the various engine combinations) and slippage in the converter itself makes for inconsistent data. We obviously picked up horsepower to the tires with a transmission that didn't slip, but we masked that with a converter with a higher stall speed.
To confuse things even more, we had switched dynos. So, what looks to be a wash on the dyno is actually a huge advan-tage at the dragstrip, which is where real racing takes place. We did find an interesting piece of data when we activated the lockup converter option in this transmission/converter combination. We saw a 10hp jump at the rear wheels-to 198.9 rwhp-showing us that the slippage in the converter would have normally cost us more than 5 percent of our power.
Now it was time to take the car to the track. It was interesting to have such a capable transmission in a car more suited to getting groceries. The Performance Automatic AODE would perform fine and stay healthy in a deep-9-second car, but we were just looking to find out this car's true potential. With the wounded and weary stock AOD, the car could muster a best of 15.087-second e.t. at 92.23 mph with a 2.285-second short time. With the PA unit in place, we had a whole new animal on our hands.
On our first pass, we tried the transbrake with the street tires in place. What a mistake. It resulted in a 2.662-second short time with the car continuing to spin well into Second gear. We shut it down and immediately rolled back to the line. We settled on forgetting the transbrake and just concentrating on driving the car out of the hole. With that strategy in mind, we went a 2.206-second short time and 14.638 seconds at 94.42 mph through the quarter-mile. We continued to concentrate on finding just the right launch (leaving with the converter flashing to 2,500) and pedaling the car until full traction was reached; then just stand on the gas and click the gears to the finish line.
We eventually mustered a 2.104-second short time with a 14.336 e.t. at 95.71 mph. The great thing was that there was at least five-tenths given up to traction. With slicks or drag radials, this is an easy mid-13-second car. With the nice, firm shifts, all we had to worry about was not overshifting from Low into Third (something that is easy with the stock shifter) and clicking the toggle switch for the lockup around 4,500 rpm in Third gear.
After kicking this car around for a few hundred miles, we can honestly recommend this transmission-and-converter package to anyone looking to take an automatic car to the next level. Our test vehicle represents the absolute minimum of performance that you would want to use this setup in, while something such as a blown, 500-rwhp street car would love this transmission. It's also something you can grow into, which is where we're at right now. Next up for our little notchback may be that GT-40 intake and a Vortech S-Trim package we've been drooling over. We can confidently say our transmission and converter will be the last of our worries for a long time.