Real diff between A9L and A9P???

[71vert-pga]

Ok, maybe a dumb question but... How does an ECU made for a 5 spd car perform with an automatic. Are there "really" and serious drawbacks to it? A9Ls just seem to be a lot more common that A9Ps.

I'm gathering parts to put an '89 efi system on my '71 302. Have just about everything but the computer and the maf sensor.

 

[5.0Droptop]

I run the a9p with a t 5 tranny. I like it. I have read that the a9p has a better timing advance curve than the a9l

 

[Venom4.6]

You can't use a 5 speed ECU with an automatic setup.

 

[71vert-pga]

How come?

You can't use a 5 speed ECU with an automatic setup.

Why? What does the A9P do for autos that the A9L does not do? They don't control the transmission, at least not prior to '94.

 

[TIMMY2734]

really no reason whatsoever that you cant.... assuming its just the timing curves that are different, its all the same.

 

[90mustangGT]

Actually they do if your car runs a AODE. Now a regular AOD or a C4 or an auto with a manual valve body it would not matter.

I always thought A9L was the one you want to get. Mine is A9L and works good for a computer controlled car.

 

[TIMMY2734]

The AODE uses a completely different computer.

 

[71vert-pga]

So then, does it really matter if I use the A9P or A9L? Sounds like it doesn't.

 

[BelueLX]

A regular AOD (non-E) and def a C4 isnt even computer controlled if Im thinking right. I think people are just trying to sell their A9P computers. I honestly have no idea why they wouldnt be almost exactly the same. If I knew someone with an A9P I'd let them swap my A9L in at the track and see what the big deal is but its on ebay right now... oh well. My A9L

 

[71vert-pga]

So, no one out there has tried this?

 

[Venom4.6]

Why? What does the A9P do for autos that the A9L does not do? They don't control the transmission, at least not prior to '94.

In my first post, I was just quoting what I have read in my Mustang Technical Reference Book and also what I have been told. The book was written by Ford so I'm going by that.

 

[88 Fox GT]

An automatic tranny can not use a manual computer (A9L). The computer has none of the programs it takes for the tranny. I don't think the AOD is fully electronic, but I'm sure something is electronic in them.

The reason an automatic computer (A9P) can be used with a manual tranny is because the manual tranny only needs a vehicle speed sensor to work, nothing else. Which the A9P already has a program to read the VSS.

Actually, I think this whole "automatic vs manual computer" thing is alot more serious on 94-95s because the auto is FULLY electronic.

 

[Venom4.6]

An automatic tranny can not use a manual computer (A9L). The computer has none of the programs it takes for the tranny. I don't think the AOD is fully electronic, but I'm sure something is electronic in them.

The reason an automatic computer (A9P) can be used with a manual tranny is because the manual tranny only needs a vehicle speed sensor to work, nothing else. Which the A9P already has a program to read the VSS.

Actually, I think this whole "automatic vs manual computer" thing is alot more serious on 94-95s because the auto is FULLY electronic.

That's what I understand also. It has to do with the harness and a few other things.

 

[drgn5.0]

the a9p has more total timing then the a9l, i think it was like 31 vs 26. or somewhere around there.

 

[jrichker]

I have used an A9P in my 5 speed, so have a lot of other guys who did the AOD to 5 speed swap. It works fine, no problems.

I have not known anyone who used an A9L in an AOD. Supposedly it doesn't work, and makes smoke, but I cannot verify that. All the inputs and outputs for the computer are the same for both cars.

 

[casey4093]

I'm running an A9l in my 87 5.0 with an aod When I first put it in there it ran excellent, but I'm having some other problems now not computer related. The computer will work!!!

 

[71vert-pga]

Does this mean that no one really knows?

I'm not looking for the fastest or quickest computer. Just trying to understand what REALLY makes them different.

Edit: Sorry casey, I just missed you. Thanks!!!

 

[PNY PWR]

My car came from the factory with an A9P and a 5spd.

 

[Lylebrewer]

I cannot speak about what each type of computer does internally. Ford kept the code secret for many years. I have always heard that the A9L's are desirable. I can speak about what the differences between AOD's and AODE's.

I have owned both an 89 GT with AOD, A 95 GT with factory AODE and a 94 GT that came with a T-5, that I converted to AODE. Also owned a 79 with SROD, a 84 and 86 with T-5's.

The AOD transmission used in the 86-93 mustangs is not electronically controlled in any way. The gear shifting is determined by the governor in the transmission (hydraulic-mechanical). This transmission had a direct drive in 3rd gear and 4th (overdrive) that bypassed the torque convertor (This is the shaft that will shear in really high horsepower racing). I just walked out to the garage and looked at my AOD that I just pulled from my wrecked 89. (I am in the process of moving all the 89 V-8 parts to a 92 4 banger body). The only direct electrical connection to the transmission is the reverse back-up light switch. The AOD has an external speed sensor that is mounted on the tailshaft. Nothing else electical at all. There were no AODE transmissions installed in mustangs prior to 1994.

The 94-95 302 mustangs used the AODE transmission which was derived from the AOD but is completely electronically controlled by the Engine Computer. I did a T-5 to AODE conversion on a 94 GT and had to swap from the Manual transmission computer to the Auto Transmission Computer (along with a few other parts). The AODE's shifting is contolled by the computer via two solenoid valves in the tranmission. The lock up is controlled electonically by the computer also. The TV line pressure is controlled by the computer also and the computer monitors fluid temp and changes the pressure based on fluid temp. It still has the same external speed sensor as the AOD transmission. for the cruise control. The AODE electrical functions are superior to the AOD but are not practical to adapt to the 93 and earlier mustangs. I believe someone makes an external controller for use with the AODE in Non-factory applications.

One of the nice things the AODE can do is: My 94 GT with AODE trans will unlock the torque convertor under mild acceleration on the highway without downshifting to 3rd.

I have the factory manuals for the 89 Mustang and the 94 Mustang. This post is based on information from the manuals.

 

[Js5ohLX]

I run a A9P. It does not retard timing between shifts, that is the only difference between the two. A9P is acutally better. With a A9L, I'd get a slight hesitation when I'd shift, with A9P, no hesitation. Oh yeah, the AOD has NO electronics. The AODE is the one with electronics.