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

Starter
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 applications.

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 stuff.

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 (148, 157, and 164 teeth). The 148 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 not.

Starter
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 place.

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 (http://www.windsor-fox.com), 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 descriptions.

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 http://www.baumannengineering.com/. This sight also has a good overview of the AOD and other Ford automatic transmissions.

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"

Notes: "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) 148 teeth - ?

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 housing:

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

Notes:
- 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  WR     Stock  WR     E4OD
     C4     C6     C6     AOD    AOD    
1st  2.46   2.46   2.72   2.40   2.84   2.72 
2nd  1.46   1.46   1.54   1.47   1.55   1.53 
3rd  1.00   1.00   1.00   1.00   1.00   1.00 
4th  ----   ----   ----   0.67   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
     WR     CR     SROD   SROD   BW     BW     RG     RG     RG     BW
     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

Notes:
- 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: Transmission".
- 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.

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