[Dan Case]

A very early, see time frame above, HP289 engine prepared for installation into a new Cobra chassis is shown in a factory photo with an iron cased transmission attached. The very large engineering number stenciled, the picture is in black and white but Borg-Warner used bright yellow paint for the number stenciling, on the right side of the transmission case reads C3AA H. The C3AA-H transmission is one model used during part of the 1963 model year for 427 c.i.d. powered Ford Galaxies. At least some 1963 model year 427 Galaxie transmission models had oiling grooves cut vertically into the faces of gears. This detail was unique to 1963 427 Galaxie transmission. It is not known if the C3AA-H model used grooved gears or not. To add to the confusion between the Ford listings and the findings of the 427 Galaxie owners group five (5) different transmission assemblies as possible for 427 powered Galaxies in the 1963 model year: C3AA-H, C3AR-J, C3AR-K, C4AR-N , and C4AR-S. I presume all these versions used Ford ten tooth spline inputs. At this time I have no idea what the engineering specifics are for all these versions.
A related subject is clutch and pressure plates.
23 Spline Disc Springs Pressure Plate Diameter
1962 221 heavy duty C20Z-7550-A 6L-6S C20Z-7563-B 10½”
1962/64 221/260 C20Z-7550-C 6L-6S C20Z-7563-D 10”
1962 260 heavy duty C0AA-7550-A 8 C20Z-7563-B 10½”
1962 260 B8A 7550-C 8 C20Z-7563-D 10”
So what clutch system did AC Cars used with the 221 2V engine and what did Dean Moon’s shop used when engine XHP-260-1 was installed in CSX2000 in California. We have no idea, either could have been one of the above or a prototype and or preproduction of what would become the 1963 model year HP289 assembly or even some type aftermarket set.


Cobra wise, all other Ford and General Motors (GM) (K set) cars excluded:
B set = standard passenger car gears, also used in Cobras 1962-63.

XCO-270 transmission set, origin unknown at this time.
J set = standard passenger car gears metallurgically, may or may not have gotten into new Cobras.

K (high nickel) set = installed into aluminum cased Cobra transmissions, street and race, introduced sometime in the CSX22xx range it is believed, example CSX2246 had a K set originally, my black car CSX2310 was fitted with a K set. (The K gear ratios originated in some high performance GM cars.) Listed as the alternate gear set in the February 1964 Cobra reconfirmation of registration for roadsters and coupes with the Fédération Internationale de l'Automobile (FIA) race sanctioning organization.
L (high nickel) set = installed into aluminum cased Cobra transmissions, street and race. Listed as the standard gear set in the February 1964 Cobra reconfirmation of registration for roadsters and coupes with the Fédération Internationale de l'Automobile (FIA) race sanctioning organization.

M (high nickel) set = introduced into aluminum cased Cobra transmissions, race and maybe street, introduced sometime in the CSX23xx range it is believed, it is believed that the later the chassis was the more likely it was fitted with a M set. Legends says they were called “Sebring” gears because SAI first used them in their race cars at the 1964 Sebring race. The Feb. 6, 1964 reconfirmation of what was submitted to the FIA (with pictures of CSX2138 and the first Daytona Coupe included) shows L gear ratios standard and K ratios as an alternative. The M ratios are not listed at all on that document. SAI was into finishing late CSX22xx and early CSX23xx chassis at the time. My black car (CSX2310, end of March 1964) came with a K set.

The tough part to deal with is that chassis were not finished in order so it is meaningless to think that since car CSX2xxx was fitted with "such and such" that chassis CSX2xxx±1 or 2 or x received the same part or assembly. Early made parts and or assemblies can be in most any car but late made parts or assemblies cannot.

Physical Information
The original transmissions fitted to Cobras, all confirmed models, had an overall assembled case length of 27 3/8 inches including the 1/2 inch spacer between the cases. This case configuration is the same as was used in the 1962-64 Galaxie or big Mercury and the 1963 Fairlane T10's. Cobra required and used the early narrow bolt pattern case design because all manual transmission equipped cars fitted with 5 bolt bell housing engines. The casting numbers on the narrow pattern T10 main cases are T10 B-1 (iron) and T10 L-1 (aluminum).
(Note: 1965-66 six bolt bell housing engine Ford version of T10 main case will fit a 1962-64 five bolt engine bell housing because it has both the early and late sets of mounting holes. There is a problem however as the transmission front bearing retainer will need to be changed because the five and six bolt bell housings each use bearing retainers with different outside diameters where they fit into the index hole in the center of the back of the bell housing. The five bolt bell housing has a smaller diameter index hole than the six bolt bell housing, so a five bolt bearing retainer will not fit snugly into a six bolt bell housing and the six bolt retainer will not fit into a five bolt bell housing because it is too big. One has to be aware of this because the transmission front bearing retainer fitting snugly into the hole in the back of the bell housing indexes the transmission main shaft centerline to the engine crankshaft centerline and a loose fit won't index the centerlines properly. While the transmission is out, it is a good time to check the bell housing runout to ensure the centerline of the hole in the back of the bell housing lines up with the crankshaft centerline as the maximum per Ford specs is 0.015 inch and some aftermarket scattershields have been found to be off as much as 0.125 inch, which is 1/8 inch! Bell housing misalignment can result in premature pilot or front bearing failure or a catastrophic clutch failure.)
The correct Cobra and Galaxie tail housing measures 17 3/8 inches front to rear and the tail housing casting numbers are T10 B-7 (iron) and T10 L-7 (aluminum). The shifter mounts to the Cobra tail housing with 3 bolts in an "L" pattern that has the vertical part of the "L" toward the front of the tail housing and the center of the top front bolt hole for the shifter mount is 4 1/4 inches from the front of the tail housing. The shifter assembly is a 1962-64 Galaxie / Fairlane T10 unit with a short, straight Cobra unique ever.
(Note: Contrary to mythology the short style Sunbeam Tiger shift lever is not the same as a Cobra’s. The Cobra and Tiger lever assemblies use different mounting fasteners and ancillaries. The Cobra lever assembly has no provision for rubber isolation mounts while the Tiger model does.)
The Mustang, Falcon or Comet T10 tail housings are 3 inches shorter than a Cobra unit and the shifter is not in the right location, so neither the tail housings or shifters will properly fit a Cobra. The 1964 Fairlane T10 tail housing has the correct shifter location, but it is about 1 1/2 inches shorter, so to use it in a Cobra will require a longer driveshaft.
The 63-64 Galaxie or 63 Fairlane T10's fit a Cobra and the ones from the 406, 427 and Hi Po 289 cars are close ratio units as are many from the 390 engine cars. The other Galaxie and Fairlane T10's and virtually all of the Mustang and Falcon ones were originally wide ratio units with the exception of the relatively few units with the "M" ratio gears used in the 1965-66 Shelby GT 350's.
Borg Warner identifies the various T10 gear ratio sets with a letter designation and the first gear set to use that particular combination of ratios has that letter assigned to the cluster gear because often the cluster alone is unique to that particular gear set. For example, T10 B-8 is the part number assigned to the first Ford T10 cluster gear and it denotes the "B" ratio set. The other close ratio Ford cluster gears are T10 J-8, T10 L-8, T10 M-8 and the T10 K-8 used in some Cobras. Often times only one gear on the cluster itself makes it different from the other gear ratio sets as can be seen farther below where the cluster gear tooth counts are shown. The quickest way to tell for sure what gear ratio set is in a particular Ford T10 is to count the teeth on the middle two gears on the cluster to identify which cluster gear it is.
Likewise, the first time any of the other 1st through 4th gears are used, it receives the letter designation of the first cluster gear it is used with and then keeps that designation regardless of the other gear sets it is used with. All of the 1960's Ford design T10 first gears are 36 teeth except the wide ratio Q first, so they will interchange between the various Ford close and wide ratio sets. For example, T10 E-12 is a nickel alloy first gear first used in a GM application and it is also the first gear for the L, M, and K nickel alloy gear sets and it will also fit the non nickel alloy B, J, H and sets.
The close ratio Ford input shafts are all 26 teeth except the GM "K" input used in some Cobras, so they will interchange between all of the Ford close ratio sets except for the K set. Be aware that the input shaft length on the B and L inputs is a bit shorter and they measure 8 1/2 inches in length because they are for use with the 390, 406 and 427 engines. The B and L inputs can be used with a 260 or 289 by using the factory Ford extended pilot bearing used in early Broncos (C5TZ-7600-D) or by adding 3/8 inch to the pilot tip, which extends it to the small block length of 8 7/8 inches.