AOD Valve upgrade

[BobCarter]

I'm looking for guidance from folks who have paired a 351W (~400 hp) with a AOD transmission. I will be building my MK IV as a driver but don't want to run into a problem with a sluggish response off the line and shift points that do not match the engine power band. My fear is that the trans. will be shifting at engine speeds (torque points) that are not optimal (I don't want a "bogged down" engine). I have read about the inability of selecting second gear with the stock AOD configuration, so it may be necessary to change the valve setup which will allow manual selection of all 3 gears and OD. A Lentech street terminator valve set appears to be an option.
Here is a summary of my running gear:
351W (torque peaks ~4500 rpm), basic torque convertor (~2500 RPM Stall), AOD (1st =2.4, 2nd =1.467, 3rd 1.0, OD 0.667), rear end 3.31, rear tires 315/30/18 (25.4" OD)
Here is a sampling of engine revs. at different travel speeds based on the above IF I could choose the driving gear:
In first at 30 mph engine turns ~3,150 rpm
In 2nd at 50 mph engine turns ~3,200 rpm
In 3rd at 60 mph engine turns ~2,625 rpm
OD at 70 mph engine turns ~2040 rpm
Here is my question- Should I stay with a stock AOD (will its shift points be a good match?) or should I change the valve body to a Lentech Street Terminator which will allow me to manually shift through the gears when I want to?

[CraigS]

I can't help w/ the TC stall speed but will say this. I wouldn't even question installing the Lentec or similiar. I know a lot of the new auto trans in todays cars are really good, but I don't think an AOD is in that catagory.

[BobCarter]

I can't help w/ the TC stall speed but will say this. I wouldn't even question installing the Lentec or similiar. I know a lot of the new auto trans in todays cars are really good, but I don't think an AOD is in that catagory.

ouch.

[CraigS]

Sorry Bob if I worded that wrong. Didn't mean anything negative at all. Just thinking an AOD was designed a long time ago, probably mostly for something like a Crown Vic, so it would certainly be a much better trans w/ some modern tech added to it. I looked at the Lentec website and saw some really cool stuff. I wasn't clear though if they have both a manual shift and the option for full auto in anything other than their base model valve body.

[6t8dart]

I have an AOD, but never heard of Lentech.

[sread]

I have an 86 Mustang w/ Kenne Bell supercharger and AOD. I rebuilt the trans myself several years ago and did several mods including TransGo shift kit, Ford Racing wide ratio gear set, high strength input shaft, super servo, etc. Unfortunately, the trans is still not very satisfying to drive. The most frustrating part is the screwy shift points (way too early) and the inability to manually control the 2-3 shift. The next items on my list are a real converter and a custom valve body. Lentech has been around quite a while and is certainly one of the innovators in AOD stuff and they have a unique system for modding the AOD but it gets pretty expensive. Somebody else to look at is Silver fox - he specializes in AOD mods and is pretty well known in the mustang community. (google silver fox valve body).
If you stick with the AOD I would definitely consider getting rid of the 2 piece input shaft and go with a non lockup convertor.
The thing is, by the time you do all this stuff you could have bought a modern trans and use a stand alone controller and probably be more satisfied with the end product. If I was starting from scratch I think I would go that route

[BobCarter]

sread- Thanks for your input. I wonder if we could get shift point improvement by adjusting the governor. I have seen some comments on this approach but most are using a governor with a very high RPM shift point (~5500). That would be an interesting area to investigate. I like the Lentech approach since it gives the option to choose the gear you want to hold in and still have the full auto capability when you want it. Guess if you have the money you can get a properly "tuned" and friendly driver with modifications to a standard AOD. The trick is to know what to spec and who to have perform the modifications.

[BobCarter]

sread- Tell me more about which modern transmissions you would look at if you were going to put it into a FFR MK IV behind a 351W, and what is involved in installing the control. Also, why drop the locking OD shaft if im not going to race the car?

[sread]

I would look in to the feasibility of using the 5r55 - the current 5 speed auto used in the late model mustang. My wife's car (09 mustang) has this trans and it feels pretty good. I'm not sure if it will bolt up to the early small blocks though - it seems that I read somewhere it would but may be physically larger -should be easy enough to find out though.
Barring that, I would go with the AODE/4R70W...basically just the most modern version of the AOD which is electronically controlled.
As far as lockup versus non lockup there is always debate over it but I believe it makes the car more responsive in the top 2 gears. Lockup is really just for efficiency (gas mileage), probably not a concern in a car such as this.
I think you are correct in your statement about being able to obtain a great shifting AOD if you have the money and know who to go to and what to ask for. It can be an expensive learning process though. Take Lentech for example - they seem to have a pretty good reputation but a little searching can still find dis-satisfied customers......though that is somewhat the nature of the internet. Even though they offer a warranty on their products/services, when you have to r/r the trans, ship it back and forth to Canada, on your dime , the value of any warranty diminishes pretty rapidly.

Anyways, here is a cut/paste from a mustang forum that gives a good overview of the various versions of the AOD and covers some of the evolution , although keep in mind this article was dated 2008 but I think it is still pretty accurate.


The Automatic OverDrive (AOD) transmission was introduced in 1980 as an answer to demands for higher fuel economy, lower vehicle emissions, and improved vehicle driveability. The AOD was a new transmission design into which various design features of existing Ford automatic transmissions were incorporated. The AOD was one of the first transmissions of its type in the automotive industry and also one of the simplest by design.
The AOD gear train design was based on the gear train of the FMX/Cruise-O-Matic transmission which (in one form or another) has been part of Ford's automatic transmission history for decades. This gear train incorporates a compound (six-pinion) planetary gear unit, utilizing one planetary carrier with a set of short and long pinions, rather than two or three single planet carriers. This design was probably used because of the minimal changes needed to "add" overdrive to it. In fact, the FMX, AOD and AOD-E/4R70W are the only modern Ford transmissions which share the compound planetary design.
The reasons for using an AOD (or AOD-E), instead of a C-4 or C-6 transmission in your performance vehicle are obvious. The primary advantage of using an AOD is the potential for fuel efficiency with no resultant sacrifice in performance, thanks to the 2/3-1 overdrive ratio which made the AOD a clear choice for Ford Motor Company, as well as its customers. For example, even a steep 3.73-1 rear axle ratio becomes a 2.49-1 ratio during fourth gear cruise (3.73 x 2/3 = 2.49), allowing about 1000 less engine RPM at highway speeds. Not only does the AOD provide a better cruising ratio than a three-speed automatic, but it also serves to further increase efficiency by bypassing the torque converter in fourth (and partially in third) gear through the direct input shaft. This is a precursor to the A4LD, E4OD and AOD-E/4R70W transmissions which use a converter clutch to perform the same function under EEC control (providing much better performance).
The AOD-E/4R70W is the latest and best Ford performance transmission, and in our opinion, represents the foreseeable future of performance rear-wheel-drive automatic transmission technology. The beauty of the AOD-E/4R70W is that it retains all of the AOD’s good features while improving the weak points (some of which can be improved in an AOD by using AOD-E parts). The AOD-E incorporates an enlarged two-inch-wide overdrive band, thereby eliminating an obvious weak link as well as providing some of the previously mentioned upgrade parts for the AOD. Another feature that is greatly improved from the AOD is the "lockup" or torque converter bypass system. Instead of the weaker concentric input shaft system of the AOD, the AOD-E/4R70W uses an actual clutch in the converter to provide lockup under EEC control, rather than the fixed "60% lockup" in third and "full lockup" in fourth gear system of the AOD. The stronger input shaft and greater flexibility of this system are further enhanced by the fact that the converter clutch may actually be partially applied or "slipped" under electrical PWM (pulse-width-modulation) control from the EEC PCM. Unfortunately, the lockup system from the AOD-E cannot be transferred to your existing AOD, but vendors such as Precision Industries and Art Carr Transmissions provide high quality input shafts and torque converters that can either strengthen the inner (most likely to snap) input shaft or eliminate the AOD’s "lockup" feature altogether (as in the case of Art Carr’s solid input shaft, which bears a strong resemblance to the factory AOD-E input shaft). Finally, the 4R70W (AOD-EW) wide-ratio gear-set can be transplanted into any AOD or standard-ratio AOD-E application for greater first and second gear pulling power.

[silver_pilate]

When I was modifying my old '91 GT, I started with a TransGo shift kit, and it was ok. I later upgraded to a Lyntech valve body with electronic OD delete, and it was a great setup. It shifted like God was kicking it in the bumper from 1-2, and to a lesser degree from 2-3, which could bring up a traction issue with a really light car and lots of power. I ran it behind a 347 stroker without issues. I also ran a 2700 rpm stall torque converter from Precision Industries.

The weakest link on the AOD has always been the overdrive. When you're running all out, there is no way to stop it from shifting into OD without a modified valve body. That's a lot of wear-and tear on the weak OD bands, so the electronic OD delete was great. I had manual 1-2-3 and then flipped a switch when I wanted OD on the highway.

--nathan

[Retirement Toy]

Look into the Tras Go Hi Rev kit. Installed it in my car n made a huge difference, especially in the 2-3 shift. Living in Southern California I love the AOD.

[Mustang Man]

The 5R55 is a BIG trans. It also has a weird mount for the crossmember. We used on in our '68 Mustang project and had to fab a custom crossmember mount. These are electronically controlled and the software out there has a steep learning curve (laptop setup only)...

If you're looking for an electronically controlled trans that will fit I recommend the 4R70W. It is a wide ratio trans, with all the updates the AOD should have had. You can control it with a small aftermarket box that allows shift feel, shift point, lockup, etc. to be controlled by simply turning a knob. Check out Performance Automatic and their Smart Shift setup.

As for those using an AOD already, they can be built to take power and shift nice, but that gets expensive. I have a full Lentech built AOD in my Fox Mustang and love the ability to shift a full 1-2-3 pattern and use OD with an electronic lockout.

That said, you can manually shift your near-stock AOD by doing the AOD Shuffle (a quick Google search will explain how to shift the selector and when).

HTH...
Mark