FMX to AOD swap. Complete report.

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luxstang

Well-known member
Joined
Dec 23, 2010
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Location
Luxembourg / Europe
My Car
1972 Mustang Convertible
So, finally the Mustang is back on the road.

Maybe some of you noticed the update on my "idle pressure to high" thread. It turned out it was a stuck valve in the valve body. Once that was taken care of everything went smooth.

I'm gonna post both the effect of the swap and the parts we needed (and did not need). The latter is important because the Internet is full of "you need this" and "you don't need that" and in the end we were none the wiser.

Before we start, let me remind you some basics on my car: It has a 351W from Ford Racing, the stock FMX and 8 inch rear axle.

All the info below was true for MY car. Don't blame me if it turns out to be different on yours. :)

The suppliers listed below are the ones I bought from. There are others out there, you may wanna check with them. The links are for better reference.

Before and after:

It is amazing how much of a difference it makes. The first three gears are the same in ratio on the AOD and the FMX, so not much difference there. But as soon as the OD kicks in it's a different world. No engine noise, no exhaust noise, only the wind noise on the convertible top.

One ting to remember is your rear axle ratio. Mine is a 3,0:1 which is a little low for this setup.

At 35 mph You will have a little under 900 rpm, which is actually idling rpm.

But, on the other hand, it is cool for freeway cruises.

Remember, I am in Europe and can have fun on German autobahns. :)

When going 110 mph, rpm is 3000!

At 65 mph it is 1700 rpm instead of the previous 2500 rpm with the FMX.

I will change the rear axle ratio to a much shorter one, probably 3,8:1 after I got the car on the dyno. Then I will know at what rpm the engine delivers best and I will match the rear ratio accordingly.

Oh, by the way, the positions of the stock shifter lever can be made to match precisely. It takes a little setup but no modification is necessary.

Parts I needed:

Lokar KD2AODHT - Lokar Hi-Tech Kickdown Kits

http://www.summitracing.com/int/parts/lok-kd2aodht

Lokar SRK-4000 - Lokar Throttle Cable Brackets

http://www.summitracing.com/int/parts/lok-srk-4000

Lokar ATA-1000 - Lokar Ford AOD Selector Shaft and Arms

http://www.summitracing.com/int/parts/lok-ata-1000

We ended up making a custom part and did not use this one. Reason is the hole in it was too small to accept the original shifter rod.

It was also pretty hard to align the shifter positions with this one. You may wanna try the one with only a slot and no hole, maybe that one will work better but I can't say for sure. Link:

http://www.summitracing.com/int/parts/lok-ata-1001/overview/

Ford Racing M-4841-B - Ford Racing Transmission Yokes

http://www.summitracing.com/int/parts/fms-m-4841-b

My FMX had 32 spline and required this new yoke. Problem is that it is a 1330 yoke and the driveshaft had 1310 ones, so we also needed:

Ford Racing M-4635-A - Ford Racing U-Joint Conversion Kits

http://www.summitracing.com/int/parts/fms-m-4635-a

From http://www.transmissioncenter.org/classic_mustang_to_aod_conversion.htm:

#29 CARBURETOR ADAPTER

FOUR FORD TORQUE CONVERTER NUTS

Inspection plate (for bottom of bellhousing)

New AOD conversion crossmember

(you can modify the existing FMX crossmember to fit but this is a direct replacement and much sturdier than the flimsy stock crossmember. Plus I think it is not a good idea to cut parts off of structural parts. By the way Summit have their own version of this part but as I ordered other parts from PATC I got this from them too.)

AOD conversion trans mount.

Things we did NOT need:

OD NEUTRAL SAFETY SWITCH PIGTAIL as that switch is built into the shifter on a 72 Mustang.

New speedo gear (the stock one fit and works precisely)

Engine block off plate. The original one from the FMX worked fine, only the inspection plate at the bottom did not fit and needed the aforementioned replacement.

New starter. Although many posts on the web say you need one, we did not. The stock one fit perfectly.

New flexplate. Stock one worked fine.

New shifter and new shifter rod (and rooster comb or whatever shifter related parts). The stock ones work perfectly and the positions of the shifter match.

Modifications:

We needed to shorten the drive shaft for about 3/4 inches and the transmission cooling line has to be reworked. The front one will fit but the rear one will need to be shortened.


Here are a few pictures:

First, the new transmission crossmember (and mount). Sorry, it's a pretty crappy cell phone pic. you can see how this is much better than the original flimsy crossmember used by Ford. This looks like it even adds rigidity to the seat platform area of the chassis compared to the original one.

IMG_4008.JPG

Here's a pic of the cooling lines before they were shortened. You can see the in and outlets on the trans and how one line will fit and the other one goes all the way to the rear of the trans body and will need to be shortened.

IMG_4009.JPG

Here's the Lokar Selector Shaft. Compare the diameter of the hole to the rod and you see that it won't fit.

IMG_4013.JPG

This is the custom made part that replaces the Lokar thingy.

IMG_4042.JPG

 
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Awesome! I will be doing this very soon, I have all the components sitting in the garage ready to go.

 
Glad it all worked out so well. How about trans lines. Did you need to alter yours?
Look carefully. The trans lines needed to be shortened. :)



did you keep the stock torque converter or go with a different one?
Good question. I used the one that came with the AOD.

To be honest, after driving it for two hours today, I think the car has less power than before. It used to take the gas pedal better.

I may be wrong because I had the car sitting over the winter and I did not drive it got 3 months but something tell me it lacks power.

Could be the torque converter.

 
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Could be the torque converter, but it could also be just a perception. Does your gas pedal feel like it takes more pressure to push it down? MIne did, due to having a TV cable versus the kick-down lever.

 
Could be the torque converter, but it could also be just a perception. Does your gas pedal feel like it takes more pressure to push it down? MIne did, due to having a TV cable versus the kick-down lever.
Not really. The motor revs but there seems to be some drag in between the motor and the wheels. Does that make sense?

 
You don't mention changing the torque converter and it should have the same reaction as with the FMX considering the gear ratios are the same. Is it up shifting too quickly?

I used an 1800 street fighter in my 69 vert with a 3.55 TruTrac rear end. IMO, its a really nice combination for get up and go and highway cruising.

 
Could be the torque converter, but it could also be just a perception. Does your gas pedal feel like it takes more pressure to push it down? MIne did, due to having a TV cable versus the kick-down lever.
I noticed that adding the TV cable to mine has resulted in requiring more effort to cycle the throttle than before I'd hooked it up. I was a little concerned over that because I was mostly just blipping the throttle with my hand, but when actually got in the car to move it onto the trailer, I didn't notice any crazy extra effort needed to push the gas pedal... it kind of feels just about right, actually. I was kind of expecting it to be really tight, but not so bad.

I can't speak to the stock converter being any more or less slushy than what was with the FMX, since mine was all seized up and nasty. I do know that my AOD's previous owner had no complaints and just wanted a 5-speed - it ran just fine, otherwise.

Luxstang - good to know about the rpms at speed. I used an rpm calculator to get a WAG on what to expect, and it sounds pretty much spot-on. What is your overall wheel diameter? I was using 27 inches as my wheel diameter to get the 1700 rpm @ 65mph statistic.

Excellent job! ::thumb:: I might just get that cross-member for mine, since I simply notched my FMX cross-member to clear the pan.

 
It's definitely shifting up too fast.

I was thinking too that there shouldn't be any difference since the gear ratios are the same but the car now feels heavier, less eager in terms of throttle response. It simply feels like the trans is eating HP.

As I said, I used the torque converter that came with the AOD. Don't know what it is exactly.


Oh, regarding the wheel diameter: your 27 inches come pretty close. I think mine is 26.8 or something similar. I'm typing on my phone right now but if you wanna look it up, the tire size is 285/40/18.

 
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Luxstang,

I use the same combo of a cleveland & AOD in my Model A and it goes like hell !!! I have an B&M "holeshot" converter in mine. It only weighs 2200 lbs. I have found that the TV cable (lokar also) has adjustments for the shift points. Do adjustments a little at a time either in or out not to much to possibly change the actual pressures.

Good luck.

Thanks, Jay

 
Thanks for your input guys. We'll look into that shift point issue again. Like I said, I've had the car for two days now. Maybe it needs a little fine tuning.

Right now it shifts into 3rd at 35 mph with medium acceleration. It used to go 45.

With hard acceleration it would stay in 2nd until 65 mph. Now it won't go over 50, no matter how hard I stomp on it.

We'll see after we tinkered with it.

 
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