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Some time ago an equiry was posted about upgrading the C6 'box. The trouble being that third speed is just too high for reasonable acceleration without using Kick-down.
Holding 3rd speed results in 'pinking' on an unacceptable level. Is there a suitable 4 or 5 speed replacement auto-box. Anyone got any recommendations?

My Deauville is fitted with a Trans-Go valve block which certainly peps up performance by quickly flicking into 2nd at the slightest prod on the gas pedal. This is great for spirited driving, but not for a comfortable cruise.

Posted on behalf or Roger Brotton
Original Post

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> Some time ago an equiry was posted about upgrading the C6 'box.
> The trouble being that third speed is just too high for reasonable
> acceleration without using Kick-down. Holding 3rd speed results
> in 'pinking' on an unacceptable level. Is there a suitable 4 or 5
> speed replacement auto-box. Anyone got any recommendations?

The common replacements are the AOD, AODE, 4R70W, and E4OD Ford 4 speed
automatic transmissions. These transmission all have the same 3rd gear
ratio as the C6 (1:1) and overdriven 4th gears so will have an overall
gear ratio taller than the C6 when in overdrive. The gear ratios are:

Stock Stock WR Stock Stock WR 4R70W E4OD

1st 2.46 2.46 2.72 2.40 2.40 2.84 2.84 2.72
2nd 1.46 1.46 1.54 1.47 1.47 1.55 1.55 1.53
3rd 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00
4th ---- ---- ---- 0.67 0.67 0.70 0.70 0.71

You may want to change your final drive ratio to get the desired overall
(transmission times final drive) ratio.

The AOD uses a conventional hydraulic valve body like the C4 and C6.
The AODE is a version of the AOD with an electronic valve body controlled
by the engine comouter. The AODE and 4R70W got durability improvemments
some of which can be applied to the AOD. The 4R70W is basically a wide
ratio version of the AODE and is the source of the wide ratio gear sets
available from FRPP for the AOD and AODE. Stand alone transmission
controllers are available. AOD's were used up to 1993 and the AODE was
used from 1992 to 1995 and the 4R70W was used 1993-up. The versions used
behind 5.0L and 351W engines will bolt up to the 351C.

I've not personally replaced a C6 with an AOD buit I have done a couple
of C4-to-AOD swaps which are similar. Also a friend has done the FMX-to-AOD
swap. The C4-to-AOD swap required a custom transmission crossmember but we
were able to modify the FMX mount. Since the distance from the bellhousing
face to transmission mount of the AOD and C6 are within a 1/4" of each other,
I'd expect you could slot your existing transmission crossmember to fit the
AOD. I've attached my C4-to-AOD notes below.

You should not have any problems with "pinking" in top gear. I suspect
you have other problems (ignition advance or cam timing). If you have
open chamber heads, they are prone to pinking.

Dan Jones

The C4 to AOD Transmission Swap
by Dan Jones

Over the 1994 Christmas holiday, I replaced the C4 automatic in my mother's
1971 Mustang convertible with an AOD. The main reason for the transmission
swap was to gain the benefits of the AOD's 0.675:1 overdrive gear (lower
cruise RPM and increased MPG). The car in question is powered by a mild
302 (600 CFM Holley, dual plane intake, mild cam, dual exhausts) and, before
the swap, had a perfectly good C4 transmission. While this is essentially a
bolt-in job, there are lots of little details that you should be aware of to
make things go smoothly. These details, in no particular order, include:

Procuring the Transmission
Extension Housing
Converter Compatibility
Gear Ratios
Working with Aluminum
Transmission Jack and Jackstands
Transmission Tunnel Clearance
Exhaust System Clearance
Transmission Crossmember and Insulator
Flexplate Diameter and Balance
Block Plate
Nuts and Bolts
Driveshaft and Yoke
Mechanical Interlocks
Shifter Operation
Speedometer Gear
Electrical Connections
Throttle Valve Operation
Hydraulic Fittings
Dipstick Tube
Drain Plugs
Transmission Fluid
Shift Kits and Transmission Coolers

To give you an idea of what's involved in a swap like this, I've covered my
experience with each of these details in the paragraphs below. I've also
listed some comparative transmission weights, dimensions, and gear ratios
at the end.

Procuring the Transmission
If you're pulling the AOD from a car, getting all of the related bits (bolts,
electrical connector, dipstick tube, converter, yoke, block plate, linkages,
levers, shifter, hydraulic fittings, etc.), will make life a lot easier.
However, we used a transmission purchased from a friend of my Dad's who
rebuilds transmissions. The price was right ($150 rebuilt), but we had to
come up with all the bits and pieces. Because of the Christmas holiday,
getting all the right pieces was harder than usual, but we managed.

Extension Housing
When purchasing your transmission, be aware that there are two tailshaft
lengths used on AOD's. The short model is the one that is closest to the C4
in overall length. I forgot to measure it but the SVO catalog says it's 10.1"
long. The catalog also indicates the short extension housing AOD was used in
all passenger cars except rear wheel drive Lincoln Marks and Continentals (not
sure about the Town Cars), 2WD F-150 trucks built after 11/81, and 83-85 E-150
vans. Also, don't confuse the AOD with the AOD-E, which has the rear mount
located farther aft and uses an electronic valve body that requires a separate
computer (like that available from Baumann Engineering) unless you are using
an EEC-IV engine computer). There are also extension housing variations among
C4's, with a short tailshaft model (6 5/8") used on some pickups and vans.
Our C4 was the standard tailshaft model (13 1/8") that was used in most

Converter Compatibility
The AOD transmission and torque converter are a matched pair. The AOD uses a
hollow two piece input shaft (one shaft inside the other) for lock-up purposes
and requires a specific torque converter. This arrangement is used to bypass
the converter torque multiplication in higher gears (60% in third and 100% in
overdrive) for better fuel economy. This is an attractive feature when using
a high stall speed converter, since locking up the converter eliminates the
excessive slippage (and attendant heat generation, RPM rise, and increased
fuel consumption) associated with such converters. On the down-side, the
input shaft is weaker than a similarly sized solid one piece design and you
lose the torque multiplication effect.

Gear Ratios
The first three gears of the AOD and C4 are of similar ratio. We were looking
for longer legs and increased fuel economy so we left our rear end gears alone.
If better acceleration is the goal, a ring and pinion swap may be in order.
The beauty of this swap is that the AOD's 0.67:1 overdrive ratio can make a
3.73:1 ring and pinion act like a cruising 2.50:1 ratio. Come to think of
it, we've got some extra 3.50:1 gears so maybe I can talk Dad into swapping
them in one of these days.

Working with Aluminum
Like the C6 and C4, the AOD has an aluminum case so use a never-seize
compound on the aluminum threads (e.g. bolting the insulator to the case).
Also, when working with small aluminum threads (e.g. dropping the pan), I
prefer a beam-type torque wrench so I can tell when I'm approaching the
desired torque value. I don't trust the click-type wrenches on the little

Transmission Jack and Jackstands
Despite its aluminum case, the AOD is no lightweight. I measured 150 lbs
(without fluid or converter... on Mom's bathroom scale) for the tranny and
34 lbs for the converter, so a transmission jack is recommended. Get the
car up in the air as high as possible to give yourself some room to maneuver.
We used a pair of stacked railroad ties underneath each front tire and a
pair of tall jackstands under the rear axle housing.

Transmission Tunnel Clearance
The AOD is beefier around the middle than the C4, so it uses up more space
in the transmission tunnel. Our '71 Mustang was designed to swallow a C6,
so there was no problem. It might be tight on cars with narrow tunnels
(like 65-66 Mustangs), but I'm told they will fit with no problem.

Exhaust System Clearance
No problem here on our particular car (dual exhaust without a crossover).
We could have installed the AOD without ever touching the exhaust, but we
decided to unbolt the pipes from the exhaust manifolds for extra working
room. This will vary from car to car so be prepared for potential exhaust
work. When working with exhaust, it's always a good idea to have a torch
around to loosen old rusted-on bolts. Soaking in a rust penetrant is a
good idea as well. Since I had the pipes unbolted from the manifolds, I
took the opportunity to put in new exhaust donuts.

Transmission Crossmember and Insulator
The only bit of true fabricating that was required for this swap was the
transmission mount crossmember. While the AOD and C4 overall lengths are
within a half inch of each other, the mounting pad for the insulator on the
AOD is 2 inches farther aft, so the crossmember mounting point needs to be
moved an equal amount. Whether you need to buy or fabricate a custom cross
member depends on the car you're swapping the transmission into. On some
full-sized cars, it's supposed to be as easy as switching to a second set of
aft mounting holes. Since I planned to do the swap over Christmas break, in
another state, and was spending someone else's money, I decided to purchase
a custom crossmember, rather than fabricate one. I purchased it from a shop
that's now out of business but there are other vendors who carry the
crossmember. Also, a friend who swapped an AOD into his '69 Mach 1 found
an FMX crossmember can be adapted to fit with only minor modification.

Flexplate Diameter and Balance
One of the more important parts of the swap is to choose the proper flexplate
for your application. The integral bellhousing AOD requires a flexplate with
164 teeth (approximately 14 1/4" diameter with an 11 7/16" torque converter
bolt pattern) for proper starter placement and converter compatibility. The
C4, however, uses a detachable bellhousing that is matched to one of three
different flexplate sizes (141, 157, and 164 teeth). The 141 teeth flexplates
are comparatively rare, having been used in cars like the V8 Mustang II. The
157 teeth flexplates were generally used in 289/302 small and mid-sized cars,
while the 164 teeth flexplates were used in 289/302 full-size cars and
351W/351C applications. The C4 164 teeth flexplates and the AOD 164 teeth
flexplates will physically interchange, but there are two balance weights
(pre-'81 302's use a 28.2 oz-in balance weight, '81-up 5.0's are 50 oz-in),
to be concerned with. All 351W's and 351C's use 28.2 oz-in balance factors.

In my case, the flexplate in the 1971 Mustang came with 157 teeth and a 28.2
oz-in balance factor, so it required replacing. Since they both have 164
teeth and 28.2 oz-in balance factors, I was under the impression that
flexplates from either a 351W w/AOD or early 289/302 w/C4 from a full-size
car would work. Looking through the books at the parts store showed different
part numbers, and listed the 351W part as working with an AOT, not AOD,
transmission. Not knowing if the AOT indicated a subtle variation that I
was unaware of, I decided to order the early 289/302/C4/full-size part (OEM
D1AZ-6375-A, Saginaw XF15). This turned out to be a mistake. When we put
the converter and transmission up to the engine for a fit check, the modeling
clay we had put in the crank pilot showed the converter snout was barely
making contact. Apparently, there is a difference in flexplate depth. It
all would have bolted together and the starter may have even managed to reach
the flexplate teeth, but there would have been no support for the converter
and the starter would have eventually chewed up the flexplate. Procuring a
351W/AOD flexplate over the holidays turned out to be an ordeal (dealers
wanted 14 days), but it was required for proper converter snout to crank
pilot placement, while retaining the proper diameter and balance. We finally
found a transmission supply house that had the right piece in stock. We put
the 351W/AOD part next to the early 289/302/C4/164 teeth part and there was
indeed a difference in height. Since then, I have checked some aftermarket
catalogs and they show the same part number for both applications, so buyer
beware. The part we finally obtained was from Sealed Power and corresponded
to OEM E0AZ-6375-A (164 teeth flexplate, 28.2 oz-in balance factor, 351W with
AOD applications). If you're swapping an AOD onto an '81 or later 5.0, you'll
need the AOD flexplate (164 teeth, 50.0 oz-in balance factor, for 5.0 with
AOD applications). I think the OEM part number for the late 5.0/AOD is
E2AZ-6375-A, but I didn't verify this. In a pinch, you could swap (weld)
balance weights between flexplates to get the proper balance factor. If you
choose to do this, remember that the balance factor is a moment of inertia
(distance time mass) so keep the product of the distance from the weight to
the center of the flexplate and the balance weight (plus any additional weld
weight) equal to a constant (either 28.2 or 50.0 oz-in).

Block Plate
A block plate (the thin stamped sheet metal plate that fits between the
engine block and transmission housing) which matches the large AOD
bellhousing is also required. This plate provides the correct starter
location and engagement depth for the torque converter snout in the crank
pilot (assuming you have the right flexplate). We used one from an early
289 full-size application (C4 with the large bellhousing).

Nuts and Bolts
The bosses on the AOD bellhousing are thicker than those of the C4, so longer
bolts are required. We didn't have enough of the proper length (2 1/8 to
2 1/4" long bolts), so we cut down a few longer bolts to get the desired
number of threads. Use a stiff piece of wire as a gauge to make sure they
don't bottom out. You can re-use the C4 torque converter nuts on the AOD
converter but it's a good idea to use new ones since they tend to round off.
Also be aware that the AOD is a mixed standard transmission, despite what the
METRIC embossed into the pan may imply. Some bolts are metric, others are not.
Generally, the tranny internals are metric, but the places where the tranny
connects to the car (insulator, hydraulic fittings, speedo-drive, etc.) are

The original starter was retained and aligned properly.

Driveshaft and Yoke
When we first put the yoke into the tranny, it appeared we would need to
shorten the driveshaft by an inch or so. This was unexpected since the AOD
is only a 1/2 inch longer than the C4. Upon closer investigation, it became
apparent the yoke was the problem. We had to trim the C4 yoke to get it to
fit properly. The AOD yokes must be a bit shorter, so pick one up if you can.

Mechanical Interlocks
The '71 Mustang has a mechanical interlock which locks the shifter into park
whenever the ignition key is in the lock position. I'm not sure what year
this first appeared on Fords, but I know my '66 doesn't have it. You could
bypass the interlock but we kept it functional. This required removing the
TV/shifter shaft assembly from the AOD (involves dropping the pan and filter).
Using the original C4 lever as a guide, we cut a spare lever and welded it on
the shaft. This caused a problem since we were unable to remove the small
circular grommet that seals the end of the concentric cylinders of the
TV/shifter shaft assembly without damaging it. The C4 has a rubber O-ring
in this area but the AOD uses a special formed piece which, like the
flexplate, wasn't easy to find over the holidays ("Sure we've got one but
you'll have to buy the $119 rebuild kit to get it").

Shifter Operation
We retained the C4 floor mounted shifter in the Mustang. Eyeballing the AOD
and C4 shift levers, it looked like the hole in the AOD shift lever would need
to be moved a bit so we welded up the hole and drilled a new one. Once every-
thing was assembled, we adjusted the linkage to get proper engagement of the
gears and interlocks, but the pointer was off. It turns out the hole was
probably in the right spot to begin with. I believe there is a quite a bit of
variation in Ford shift levers (especially between floor and column mounted
shifters, but also between body styles), so this will need to be checked on a
case-by-case basis.

Speedometer Gear
The speedometer driven gear assembly from the '71, including bolt and
retaining clip, slipped right into the AOD. I didn't get a chance to verify
the ratios, but the speedometer operated normally. There may be some
variation (seven and eight teeth gears?) with the AOD drive gear (the gear
inside the tailshaft housing), so you may have to change driven gears for
proper calibration.

Electrical Connections
The AOD uses a four pin electrical connector for the reverse/backup lamps and
neutral sensing switch. We didn't get one with our tranny, so we soldered
some wires on and used a liquid rubber compound to insulate. If you end up
soldering, be careful not to melt the plastic housing that holds the pins in

Throttle Valve Operation
The AOD does not use engine vacuum and a modulator valve to sense load.
Instead, a throttle valve is used which moves proportional to throttle pedal
travel. Unlike a kick-down rod, the TV linkage has to operate throughout the
full travel. This is one of the most important parts of the swap to get
right. Failure to do so will cause poor shift quality and can quickly ruin
the transmission. When adjusting the linkage, it is safer to err on the side
of hard shifts. There are a several ways of implementing the TV linkage and
the linkages can be pirated from cars or trucks that came with AOD's and carbs
or throttle body injection. A rod arrangement was used on AOD cars equipped
with a carb or TBI, while a cable was used on SEFI cars. We were planning on
getting the linkage off a variable venturi (VV) carb from a local junkyard
that had a stack of them, but they had recently tossed them all out. We
ended up just adapting the kick down rod to serve as the TV linkage. The
trick is to ensure the proper range of travel of the transmission TV lever
for the entire carburetor throttle range. We examined another AOD equipped
car to get the proper lever orientation and ratios. After we finished the
swap, I noticed a friend's 1981 AOD equipped F150 pickup truck has a rod
linkage with an adjustable lever at the transmission and a threaded
arrangement at the carb that looks like it might work nicely as a swap linkage.
Remember, you'll need a way to adjust the linkage to vary shift feel.
Alternatively, you can purchase an aftermarket TV cable kits (available from
Windsor-Fox (, Total Performance, and others).
For more information on alternatives, find a copy of the May 1990 issue of
Super Ford magazine. The article "A-OK AOD" contains a sidebar on adapting
the AOD to non-stock applications. Ignore the part about your stock flexplate
and block plate working just fine and pay close attention to the linkage

Hydraulic Fittings
The hydraulic fittings on our AOD were larger than those of the previous C4.
After the existing lines were trimmed to their proper length, two adapter
fittings (1/4" (ID) pipe, 5/16" (OD) tubing) were used to mate the fittings
on the transmission lines to the AOD case. I believe the lines on our car
were not original since they looked like new and had quite a bit of excess
length. They were also harder than any factory line I've dealt with. Even
though we used the proper tubing benders and double flair tools, the lines
were very hard to work with.

Dipstick Tube
With a minor bending of the attachment bracket, the AOD dipstick tube went
in easily. The AOD tube proved to be shorter than the C4 tube and ended up
in close proximity to the export brace, so a long neck funnel was required
to fill the transmission. This will vary from car to car.

Drain Plugs
One thing I forgot to do was to install a drain plug kit when I had the pan
off. B&M makes an inexpensive kit that, along with our stock converter's
drain plug, would make it very easy to do complete fluid changes.

Transmission Fluid
AOD's take a lot of Dexron-II transmission fluid (the C4 used type F). The
Chilton's we checked for capacities quoted 24 pints (12 quarts) for a totally
dry transmission like ours.

Shift Kits and Transmission Coolers
This particular car is not subjected to much abuse so we didn't install a
shift kit or auxiliary transmission cooler. To begin with, we'll simply
adjust the TV linkage to give firmer shifts and see how it works out.
For performance applications, a friend uses the Karl Baumann shift kit and
a Thunderbird C-servo upgrade and really likes the combo. Because we might
be putting an AOD behind my brother's 351W and a friend's 351C-2V, I did some
research on AOD durability and performance modifications. I don't have time
to go into it here but there were a number of running changes made to the
AOD over the years to improve durabilty and there are several recommended
aftermarket upgrades if you want an AOD to live behind a high performance
engine. Check Baumann's web site at
This sight also has a good overview of the AOD and other Ford automatic

While there are lots of little details (and a couple major ones), this is
definitely a do-able swap, especially if you get all the related parts from
a donor car. I've included all the variations that I am aware of, but
remember your mileage may vary. As a reference, I've also included some
comparative C4 and AOD dimensions and weights, plus a bunch of gear ratios.

Dan Jones

C4 and AOD Dimensions

Overall Length (bellhousing to tailshaft housing end, flat-to-flat):
AOD - 30 3/4"
C4 - 30 1/4"

"Engine Swapping Tips and Techniques" lists C4 length as 27 3/4" (C6 length
28 1/2" or 28 3/4"). I may have measured to the end of the output shaft,
not to the end of the tailshaft housing.

Distance from Bellhousing to Insulator Mount (flat to mounting hole centerline):
AOD - 21 3/4"
C4 - 19 3/4"

Torque Converter Stud Spacing (centerline-to-centerline)
AOD/C4/164 teeth flexplate - 8 1/4" between closest studs, 11 7/16" between
farthest studs (stud pattern diameter)
C4/157 teeth flexplate - 7 3/4" between closest studs, 10 5/8" between
farthest studs (stud pattern diameter)

Transmission Lengths from "The E4OD", Ford High Performance, April 1995

Trans Bellhousing Overall Length
Face to Trans From Bellhousing
Mount Length To Tailshaft End

C4 20 1/4" 30 1/2"
C6 22 1/2" 33 1/2"
AOD 22 1/4" 30 3/4"
E4OD 29 3/8" 37 1/2"

Torque Converter Snout Diameter (from early SVO catalog)
289, 302, 351W/C/M, 400, 429/460 - 1.375"
FE series and early '68 Lincoln 460's - 1.848"

Flexplate Diameters
164 teeth - 14 3/16" (13" converter)
157 teeth - 13 1/4" (11" converter)
141 teeth - ?

Mustang II used 148 teeth flywheels and 141 teeth flexplates.

C4 Variations

C4 detachable bellhousing, case, and tailshaft housing.

Large bellhousing - smooth flair case, twin bolt circles (case to housing,
outer secures bellhousing to trans case, inner secures oil pump to case),
3 locating tabs, 14 3/16" flexplate, 13" converter, no dipstick hole in
main case (dipstick goes into right front corner of pan), used in small-block
powered large cars and light trucks.

Small bellhousing - step case, single seven bolt circle (case to housing),
13 1/4" flex plate, 11" torque converter, dipstick hole in case (seals with
an O-ring), five bolt ('64 1/2 and early '65 Mustangs, etc.) and six bolt
versions, used in small and medium small-block powered cars.

Trans-Dapt supposedly makes adapters for six bolt blocks to five bolt
transmissions (need to check on details).

Top bellhousing bolt holes are 5 1/8" apart.

"C" intermediate servo (289 hipo applications) is largest but rare.
"H" servo is next largest, used on 302 4V engines from 1968.
"A" servo is typical stock unit.

Pinto governor allows highest rpm shifts, p/n D7ZZ-7C063-C.

C5 pan interchanges with C4 and is deeper.

There was a revision in mid '70's to nine mounting bolts for the valve body,
previously used 8 bolts.

Main cases and bellhousings for large and small versions are not
interchangeable. 5 and 6 bolt small bellhousings are interchangeable between
each other (on the case side).

Entire 6 bolt (small or large bellhousings) transmissions, except for
dipstick locations, are interchangeable in many cars (some smaller cars
require the small bellhousing variant).

C5 bellhousing looks similar, but has a completely round hole in the front
pump area and is not interchangeable with C4 bellhousing.

Standard Tailshaft - 13 1/8" long, most applications.
Short Tailshaft - 6 5/8" long, some pickups and vans.

Input Shaft Spline Count (8 cylinder and some 6 cylinder applications)
'70 and later - 26 splines
pre-'70 - 24 splines

Note: Some 1970 input shafts have 26 splines on both ends ('71 and later have
24 splines on one end and 26 on the other), making them the most desirable
for drag racing applications.

Need to add C4 valve body variations (green-dot, cruise-o-matic, etc.) and
AOD shift sequence

Four and six cylinder versions are light duty (fewer clutch plates).

Some C4's (late '60s, early 70's Mavericks? need to check details) had
full-manual valve bodies.

Major C6 variations

C6 integral bellhousing (case and bellhousing are one piece) with tailshaft

FE big blocks - round bellhousing opening with top bolts 6" apart,
often have stiffening ribs on top of case/bellhousing

302/351W/351C - bellhousing opening is squared off on top, case opening
is 16 3/4" tall, top bolts are 5 1/8" apart, no ribs

351M/400/429/460 - bellhousing opening is squared off on top, case opening
is 17 3/4" tall, top bolts are 7 3/4" apart, has ribs

Transmission Weights

AOD (without converter or fluid) - 150 lbs
AOD stock torque converter - 34 lbs
C4 (without converter or fluid) - 110 lbs
C4 torque converter - ? lbs
C6 (without converter or fluid) - 140 lbs
C6 torque converter - 30 lbs small block, 31 lbs big block
FMX (without torque converter, unknown fluid level) - 160 lbs
FMX torque converter - 32 lbs
Ford-o-Matic (pre-FMX), cast iron case - 228 lbs


- AOD and C4 weights are as measured by me using a standard bathroom scale.
- FMX and C6 torque converter weights provided by Steve Grossen (also used
bathroom scale).
- Ford-o-Matic weight is an assembly line weight provided by my Dad.
- C6 weight is from "Engine Swapping Tips and Techniques" which also lists
the C4 at 109 lbs.

Ford Transmission Ratios Comparison

Stock Stock Stock WR Stock Stock WR 4R70W E4OD

1st 2.46 2.46 2.40 2.72 2.40 2.40 2.84 2.84 2.72
2nd 1.46 1.46 1.47 1.54 1.47 1.47 1.55 1.55 1.53
3rd 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00
4th ---- ---- ---- 0.67 0.67 0.70 0.70 0.71

1984 85-86 1983 1984 85-89 90/SR WC TR TR
SVO T5 SVO T5 T5 T5 T5 T5 T5 3550 3750S

1st 4.30 3.50 2.95 2.95 3.35 3.35 2.95 3.27 3.18
2nd 2.37 2.14 1.94 1.94 1.93 1.99 1.94 1.99 2.06
3rd 1.50 1.36 1.34 1.34 1.29 1.33 1.34 1.34 1.39
4th 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00
5th 0.76 0.78 0.73 0.63 0.68 0.68 0.63 0.68 0.65

TL TL cast alum T10L T10M 4+1 ROD ROD T56

1st 2.78 2.32 3.29 3.07 2.36 2.36 3.27 3.27 3.01 2.97
2nd 1.93 1.69 1.84 1.72 1.76 1.62 2.13 2.13 1.88 1.94
3rd 1.36 1.29 1.00 1.00 1.41 1.20 1.57 1.57 1.46 1.35
4th 1.00 1.00 0.81 0.70 1.00 1.00 1.23 1.23 1.19 1.00
5th ---- ---- ---- ---- ---- ---- 1.00 1.00 1.00 0.82
6th ---- ---- ---- ---- ---- ---- ---- 0.76 0.62 0.62

RBT 6 speed transaxle (Ford GT prototype)
Ratios :
1st 2.86 : 1
2nd 2.06 : 1
3rd 1.47 : 1
4th 1.18 : 1
5th 0.958 : 1
6th 0.740 : 1
Reverse 2.86 : 1
Final drive ratio : 4.22 : 1, limited slip

RBT 6-speed
Crown Wheel and Pinions
1st 2.86 2.58
2nd 2.06 1.61
3rd 1.47 1.14
4th 1.18 0.958
5th 0.958 0.807
6th 0.740 0.704 0.642 0.620

ZF 5-speed
Crown Wheel and Pinions
1st 2.23 2.58
2nd 1.47 1.61 1.72
3rd 1.04 1.14 1.32
4th 0.846 0.958 1.09
5th 0.705 0.655 0.642

- C4 ratios are from the 1966 Mustang Illustrated Facts Book which also shows
a 1.47 2nd gear ratio for certain transmissions.
- AOD overdrive ratio is sometimes listed as 0.675:1.
- WR C6 indicates a C6 with the wide ratio gear set from SVO Motorsports.
- WR AOD indicates an AOD with the wide ratio gear set from SVO Motorsports.
- E4OD is Ford's heavy duty automatic overdrive transmission.
- 1984 SVO T5 was combined with a 3.45:1 final drive ratio
- 1985-1986 SVO T5 was combined with a 3.73:1 final drive ratio
- Some 1985 T5's used 1984 gear ratios (carry over production).
- Certain 1989 T5's used 1990/SR gear ratios.
- SR T5 indicates Ford service replacement transmission for '85-up 3.35 box.
- WC T5 indicates SVO Motorsports World Class T5 (M-7003-CA, E4ZM-7003-A).
- All T5 ratios from Muscle Mustangs and Fast Ford, June 1991, "Mission:
- When comparing ratios from automatic and manual transmissions, the torque
multiplication of the torque converter must also be considered.
- The AOD provides 60% lock-up in third gear and 100% lock-up in fourth gear
(eliminates torque multiplication).
- SROD indicates single rail overdrive.
- T10 and SROD ratios from "Engine Swapping Tips and Techniques".
- SROD aluminum case gear ratios are for a 79,82,83 Mustang V8 applications.
- SROD cast iron case gear ratios are for 77-78 V8 Granada applications.
- WR TL indicates wide ratio top loader.
- CR TL indicates close ratio top loader.
- BW T10 indicates Borg Warner T10 used in some Fords.
- TR 3550 indicates the 5 speed overdrive Tremec transmission. The TR-3750S
is a proposed close ratio version which was never produced. The TR-4250
version was essentially a Reider re-worked TR-3550 and has the same ratios
as the TR-3550.
- Tremec information taken from the September 1992 Super Ford article "Top
Loader Plus One".
- RG 4+1 indicates the Richmond Gear non-overdrive 5 speed transmission
(formerly produced by Doug Nash).
- RG ROD indicates the Richmond Gear overdrive 6 speed transmission.
- Some RG transmissions are available with alternative (3.27/2.14, 4.06/2.22
4.41/2.22) first and second gear ratios.
- Richmond Gear information taken from JBA and Summit Racing catalogs.
- T56 ratios are for the Ford aftermarket version. The GM and Chrysler
versions have different ratios.
- All gear ratios are for Ford versions of the particular transmissions.
- Concerning the SVO 4 cylinder transmission ratios, Dan Malek notes:
I have yet to find a '85 or '86 SVO with those gear ratios. I know,
those numbers get published everywhere, but I have measured up at
least half a dozen original '86 SVO transmissions. I have always
found the standard 4-cylinder ratios, something like 4.05, 2.32,
1.55, 1, 0.81. Those '84 SVO numbers don't look quite correct either.
- The FMX was used 1968-81 in many Ford products and is an hydraulically
controlled rear wheel drive transmission. It has a cast iron case and an
aluminum bell housing and extension housing. It is similar in appearance
to the Fordomatic that was used since 1951 and the Borg-Warner BW8 and
BW12, but almost none of the parts are interchangeable. 1968 was a
cross-over year where the Fordomatic was used in some vehicles for part
of the year before changing over to the FMX. Rear cooler line is the
cooler return line. Band adjustments: Intermediate = ¼" servo travel,
Reverse = 1½ turns.

Balance Factor Information

1981-and-up 5.0L - 50.0 oz-in
Pre-1981 289/302 - 28.2 oz-in
351W and 351C-400 - 28.2 oz-in

4 Pin Wiring Sequence (AOD)

#33 W/PK (AOD Neutral safety)
#32 R/LB (AOD Neutral safety)
#140 BK/PK (AOD Back-up lights)
#298 P/O (AOD Back-up lights)

> From what I'm told, there's only one type stock cast-iron flywheel
> which fits the 289, 302 and 351C,-W & -M engines with a 28 in-oz external
> balance.

Ford used 148, 157, and 164 teeth flywheels on small block Fords. At
various times, 10", 10.4", 10 1/2" and 11" clutch disc/pressure plates
were used. Be aware the ring gear locations vary, requiring compatible

> After about 1987, these flywheels were balenced to 50 in-oz so
> they don't work on early engines unless you completely change everything.

The balance factor change occured in 1981 and pertained to the 5.0L/302

1981-and-up 5.0L - 50.0 oz-in
Pre-1981 289/302 - 28.2 oz-in
351W and 351C-400 - 28.2 oz-in (all years)

Also, the 164 teeth 240/300 truck six flywheels will bolt to the 351C
(and other SBF's) but are neutral balance.

> Hello, I have read that you have completed an AOD swap in a 69 Mustang using
> an FMX crossmember, I am considering swapping my spare AOD with the current
> C4, and have a bead on a cheap FMX crossmember, and am wondering if you could
> share how the FMX crossmember would be modified to bolt up to an AOD.

I did the swap from C4 to AOD in '71 Mustang convertible using a custom
crossmember. A friend swapped an AOD into his '69 Mach 1 and used an FMX
crossmember. He said it required only minor modifications (slotting the bolt
holes). Be aware there are that there are length variations in both C4's and
AOD's. The second time I did the AOD swap, I used an AOD out of a Lincoln
Town Car and found the tailshaft housing to be about 3/4" longer. The mount
bolt holes were in the same place, so only the driveshaft had to be shortened.
Also, the linkage on the transmission varies (cloumn or floor mounted shifter).

> 1. What are the advantages/disadvantages of using an AOD lock up as opposed
> to a non-lock up?

The lock up gives better fuel economy, a lower cruise RPM, and probably
runs a bit cooler. You can also run a little higher stall speed convertor
with the lock-up than you might otherwise, as the slippage goes away upon
lock-up. The biggest downside is that the input shaft is not solid and
is therefore weaker. The lock-up uses a solid shaft within a hollow shaft
that can break if you have enough torque and traction.

> Will the trans crossmember have to be moved or modified to accept the AOD?

Yes. The mount is farther aft. Dimensions in the attached post.

> 3. How easy is it to attach the AOD TV cable to a Holley 600 carb?

You'll need a special bracket and throttle valve cable. You can also
adapt the linkage from the donor car. If you can find an old variable
venturi carb car with AOD, you can rob that set-up. If your time is
worth much, there are kits ready made for the purpose.

> the aod is quite a bit larger than your C-4, although a friend told me
> that they make a smaller version now.

There are length variations to be aware of. I've done the AOD swap a couple
of times and the second time I used a Licoln Town AOD. Turns out the
Town Car tailshaft housing was about 3/4" longer than the Mustang AOD I'd
used previously. The rear mount is in the same place, so the only impact
is on the length of the driveshaft.

> stay away from the electric models.

The AOD-E is an electric valve body version of the AOD and requires a
computer for control. Karl Baumann makes a stand-alone computer for
that purpose if not running a Ford EEC-IV or EEC-V. The AOD_E recieved
a number of heavy duty upgrades, so is worthy of consideration. Also,
no TV cable problems.

> The Holly hoook ups.....I am certain that I've seen Holly carbs in both
> the JEGS and SUMMIT catalogues where they sell a special bracket ( $10
> to $15 ) to hook Holly's and Elderbocks up to AOD's.

I think you're confusing the Ford kickdown linkage brackets. The AOD's
don't use that. They use a throttle valve which requires a different
set-up (available from several places including Windsor-Fox and Total
Performance) and are closer to $75 than $15. Be aware the throttle valve
adjustment is critical. It's better to start with the shifts on the hard
side, rather than the soft side as the slippage in a soft shift can cause
trouble. I tried to adapt a kickdown rod arrangement but it never proved
satisfactory. Also, Ford used a rubber grommet at the cable connection.
If that grommet falls out, it can toast the transmission in just a few
miles. That happened to my dad and to a friend's dad. Requires a
complete rebuild.

> Any help or advice would be greatly appreciated.

I tried attaching a detailed write-up I did when I swapped an AOD in place
of a C4 in a 1971 Mustang but it was too long for the forum. An old version
is out on the web at:

Your Cobra will be different but the steps to consider are the same.
Don't try to use a 5.0L flex plate, as the balance will be wrong:

Balance Factor Information

1981-and-up 5.0L - 50.0 oz-in
Pre-1981 289/302 - 28.2 oz-in
351W and 351C-400 - 28.2 oz-in

Also, the pin wiring sequence is:

4 Pin Wiring Sequence (AOD)

#33 W/PK (AOD Neutral safety)
#32 R/LB (AOD Neutral safety)
#140 BK/PK (AOD Back-up lights)
#298 P/O (AOD Back-up lights)

Top cooler line is the cooler return line.

Here's a link to discussion on setting up the TV cable:

> Shift linkage for AOD in 65 Mustang
> Does anyone know of anyone making shift linkages for the AOD swap that are
> bolt in without having to remove the existing AOD shift arm?

I use "up" pointed lever and then just modify the stock early shift rod.
Works like a charm every time. Alex Denysenko

There are 2 types of TV linkages. The easier to work with is the older model
that came on cars with carburators. You can use the same linkage as came on
your old trans (c6 or fmx if you have a cleveland enging). The best way to set
it up is not from the WOT position but from the idle position. Usually the kick
down lever on the carb will work by just putting a longer screw in it so the
screw is just touching the throttle lever on the carb. This will give you a
good starting point. Then by screwing in the screw, you get harder and later
shifts and screwing out, you get later and softer shifts.
> How much hp/torque can an AOD take? Thinking of a mildly tuned Longchamp with
> 400hp and about the same numbers with torque.

Starting with a 5.0L V8 version, say from a Mustang 5.0L, and adding a
Baumann shift kit ( and a Thunderbird Super Coupe
servo you're probably good to 400 HP. There are guys that put serious power
through them but they replace the concentric input shaft with a solid input
shaft (stil has overdrive but does not lock-up the torque converter) and
a different valve body. Here are a couple of links with good information
on AOD/AODE upgrades:

Dan Jones
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