Besides two basic ways to upgrade your Ford overdrive automatic transmission different with heavier duty internal parts, you can improve the durability for moderate performance use without removing the transmission or doing any major disassembly.

One way to upgrade is to swap in the good, heavy duty parts out of a '98-up 4R70W as outlined below. Then you don't need the over $400 electronic control box as you would with a 4R70W. However, you then have to live with the less desirable internal lockup system of the AOD which applies lockup in 3rd and especially overdrive and which you cannot selectively turn on and off or control the application rpm. If you choose to fully eliminate the lockup altogether, you then lose highway fuel economy as well as some torque transfer in 3rd and overdrive from converter slippage which actually slows the acceleration rate by a small percent. Also, the hydraulically controlled valve body cannot be fine tuned for shift characteristics and especially shift points as well as the 4R70W. The only real way to have full control of 2nd and be able to hold it in gear manually is to use a fairly expensive Lentech valve body.

The other way is to find a good used 3.8 V6 or 4.2 V6 4R70W out of any '99-up Ford vehicle ('99-up has the best case). These have ALL the good heavy duty internal parts Ford has developed for the automatic overdrive series of transmissions, and the 4.2 unit even has the same amount of clutch plates as the V8 models which are reportedly good for up to 450hp in totally stock trim, but it has to have a car manual shift lever shaft which can be swapped by basically dropping the pan and pulling a roll pin. The 4.2 is out of a truck where the manual lever points up instead of down like car units. The 3.8 unit just has one less direct clutch plate which can easily be added. You would likely want to go thru and freshen up any transmission before you install it, anyway, unless you find a real low miles unit. It does not have the same mechanical lockup in 3rd, and the lockup can be setup to be controlled by a switch. It's a bolt in deal except for the $400+ electronic valve body control. See the AOD Parts Interchange article (also in this TECH section) for details. The electronic versions are 7/8" longer than a standard length AOD, so there will be driveshaft and mount issues.

Following the Minimum Upgrades section are the "good" parts to swap out of a '98-up 4R70W into an AOD. Ones with ** can come out of earlier models, including AOD/E. See the first article in the Tech/Transmission section of tccoa.com for all relative Ford part numbers for parts mentioned below and additional details. The Transtarindustries website has a great layout of all the parts, including the '90-'93 AOD steel forward drum, and gives Ford numbers for most of them, along with some good detailed information on application.

The AOD style pump, stator support, and forward clutch drum assembly, cannot be interchanged with the AOD/E or 4R70W parts.

For some very good technical links, see the end of the RWD Parts Interchange article also in this TECH Section.



MINIMUM UPGRADES FOR MODERATE PERFORMANCE USE

• Use Mercon V fluid. Change each ~25k miles if hi-temp climate, lots of stop-and-go driving or hard use. Change ~50k miles for less severe use or conditions (heat). For severe use/abuse/hot conditions, use synthetic.
• If you find ANY metal particle contamination in the pan, the trans should be disassembled and repaired and, a new radiator (trans cooler) is mandatory to prevent rapid wear on the ring grooves in the stator support (check CAREFULLY for wear!!) It's nearly impossible to flush all metal particles out of the cooler. Also flush the lines really well. There are aftermarket flush kits, best to use only for sludge. A remote trans filter, as shown in another article in this TECH section also helps, especially when used with a Mobil 1 small micron / high efficiency filter (many kits use the Ford Motorcraft FL1A type filters).
• DEFINITELY a Baumann shift kit.
• DEFINITELY a 2500 or so lockup stall. Mustang guys are currently hot on Edge brand. Just use a good name brand, better torque multiplication and durability. Stock AOD converters are very low stall. Some guys use a stock V6 AOD converter for a little higher stall. Stock AOD converters are not durable for rpms over about 5500. A decent budget converter with increased stall speed, durability, and a higher rev limit without ballooning can be had from www.roadrunnerconverters.com.
• A good stacked plate type trans cooler. Several good brands are available.
• "A" OD servo (or aftermarket A+ or SuperServo) most AOD have the smaller B servo.
• Install the '97-up Ford molded rubber accumulator FAZ-7H292-AA, also available at www.bulkpart.com and also available aftermarket.
• The Pressure Regulator, Boost and Throttle valves on AOD's have problems. There are Sonnax replacements - info on the Sonnax website and in various aftermarket online catalogues including Baumann (now becontrols.com).

FOR MORE THAN MODERATE PERFORMANCE USE

• '90-'93 stamped steel AOD forward clutch drum with 5 later model frictions is good to ~450 hp or it can be upgraded to 6 frictions by deleting the wave plate or by using thinner Alto brand “Red” frictions. Some say deleting the wave plate can make for uneven clamping in the clutch pack and reduced clamping force. Some rebuilders don’t like the thinner Alto Kolene treated steels as they are so thin they can get overheated and warp. The stock pre-'90 AOD has 4 frictions. AOD/E and 4R70W forward clutch drum assemblies won't work in an AOD because the shafts are different.
• Thinner '98 and up intermediate clutch pressure plate to fit 4 friction intermediate clutch. The pressure plate is stamped "4 plate". Stock AOD has 3 frictions (many trans shops will have this in good used shape priced very reasonably (from any '98-up V8 or 4.2V6 4R70W). See the TCCoA site for the proper frictions to use. Best for under 450 hp is the pre-'98 grooved frictions. The '98-up frictions are non-grooved and can hydroplane when applied unless used with an aggressive accumulator, causing slippage and glazing.
• Mechanical diode intermediate 1-way clutch (bulletproof).
• Stock AOD 7-roller intermediate sprag prone to failure especially with higher power and or abuse. '93 to '97 4R70W’s had a 14 roller intermediate sprag which is better but the mechanical diode is still considerably better and not much more. With either type, you need the aftermarket split retainer ring which prevents the retainer from coming off under higher rpm and destroying the transmission.
• '98-up reverse drum matching sun gear shell to work with mechanical diode (intermediate 1 way clutch).
• Also allows use of 2" OD band versus AOD 1-½" OD band. Early 90's pickup and van AOD's have a wider reverse drum that will take the wider OD band, but you need the matching '98-up drum for the mechanical diode . Best 2" band is stock '96 and up 4R70W band. Do NOT use Kevlar except for mainly strip use. Even with high performance accumulators and high lines pressure, they are prone to slipping under hard shifting which causes heat buildup.
• Kits are available with the mechanical diode and matching reverse drum to fit '90-up AOD/E/Ws that already have a steel reverse drum, or kits that also have the required sun gear shell that fits with the steel reverse drum are available for cast drum pre-'90 AOD's.
• Early '90's AOD or AOD/E stamped steel direct clutch drum with 6 frictions** or 4R70W drum that will take 6 or 7 OEM frictions newer/better material in '98-up frictions/steels. Later model '98-up plates are better. The thicker steels have higher heat capacity and the friction material won't wear out like the pre-'98 stock frictions. Or you can use aftermarket Alto high performance "red" frictions but because of the possibility of heat induced warping, it may be best not to use the thinner kolene treated steels.
• Stock some LSC Mk VII and Mustang V8's had 6 frictions, but cast drum, prone to wear in the shaft splines, and frictions not as good. See the becontrols.com website for a picture of a cast drum and where to look for spline wear in the drum. If this happens, the shaft can slide to the rear and block the lube holes in the end of the output shaft.
• For higher power and torque, and for more abusive driving than normal street, it is very good to install an aftermarket hardened/stronger inner direct/lockup input shaft. Stock ones can twist under high torque.
• The pistons in the older cast drums will not fit into the newer stamped steel drums, although most shops sell them as an assembly. Then you also get the new lip seals and don't have to fight installing them. Without the right tools, it's nearly impossible.

FOR MAXIMUM PERFORMANCE USE AND DURABILITY

• Wide ratio planetary gear set
  • Pre '96 gear sets, all AOD, AOD/E, and 4R70W had aluminum bushings. '96 and up 4R70W gear sets have all bronze bushings, which are much sturdier.
  For this gear set, you need either a '93 Mark VIII 4R70W output shaft hardened for use with the wide ratio gear set and has governor feed holes OR have your shaft hardened, at least where it goes in the gear set.
  
  

Electromatic Performance for Your Vehicle
Ford-AOD.com - The Ultimate AOD Transmission Performance Website
TCI AOD Throttle Valve Adjustment Instructions
4R70W Rebuild Check List
4R70W Page
AOD Intermediate Clutch Lip Seal Installer Tool
Ford Transmission Parts index: Automatic Transmission parts, Makco
Ford Transmission Forum
TCCoA.com - Thunderbird & Cougar Club of America



- macx