[Dan Case]

There are Borg Warner part numbers for each gear along with OEM part numbers for any T10 gears used in an OEM application and sometimes there is more than one OEM number if more than one car manufacturer such as GM and Ford used that particular gear. Borg Warner T10 gear numbers are relatively simple to follow as the only change in the gear part number is the letter designation itself, which is replaced with a __ in the example below:

T10__ -8 Cluster gear
T10__ -16 Input shaft (4th gear)
T10__ -11 3rd gear
T10__ -31 2nd gear
T10__ -12 1st gear
Ford T10 Close Ratio Gear Tooth Counts:
B close (1962)* L & J close** M close*** K close (GM)****
1 36 1 36 1 36 1 36 (GM 1358577/Ford C3AZ-7100-F/BW T10E-12)
2 32 2 30 2 29 2 30 (GM 1358579/Ford C3AZ-7102-E/BW T10E-31)
3 29 3 29 3 27 3 29 (GM 1358576/Ford C3AZ-7B340-A/BW T10E-11)
4 26 4 26 4 26 4 27 (GM 9771377/BW T10K-16)
C 29-23-20-17 C 29-23-19-17 C 29-25-20-17 C 28-23-19-17 (GM 9771378/BW T10K-8)

* The B gear set may have been used in early Cobras.
** L gear sets are high nickel alloy, J gear sets are not and the J sets were used in HP289 equipped Fairlanes and 390 Galaxies.
*** The M set is a high nickel alloy and also called the "Sebring" gears and was first available in 1964 for the Sebring race.
**** The K close ratio gear set is a high nickel alloy gear set originally used in GM cars (Pontiacs) from 1957 to 1963 and it was used in some Cobras. A GM clutch disc is used because the GM input shaft diameter is larger. 1st, 2nd & 3rd gears in the K set are the same as used in the L ratio gear set. Also required is a different pilot bushing in the tail of the crankshaft because the GM pilot tip is smaller in diameter than the Ford parts.

“L” T10L-8 (high nickel) = C3AZ-7113-H (cluster)
“L” T10L-16 = C3AZ-7017-G (4th)

“M” T10M-31 = C3AZ-7102-G (2nd)
“M” T10M-11 = C3AZ-7B340-C = S1MS-7B340-A (3rd)
“M” T10M-16 (4th)
“M” T10M-8 = C3AZ-7113-K (cluster)

“J” T10J-16 = C3OZ-7017-F (4th)


The Ford T10 wide ratio gear set tooth counts are provided below for gear identification purposes. The "Q" ratio gear set will not fit a Cobra because it uses its own main shaft with a different diameter on the tip that fits into the rear of the input shaft and a "Q" main shaft is not available in the Cobra length.

H wide ratio Q wide ratio (66 Mustang only)
1 36 1 34
2 30 2 27
3 28 3 24
4 24 4 20
C 31-24-19-17 C 28-21-18-18

T-10 Gear Ratios:
B XCO-270 J & L M K (GM) Mystery
(Cobra race (Cobra race 2nd alternate
alternate 1962) 02/06/64 FIA registration)
1 2.36 2.20 2.36 2.36 2.20 2.33
2 1.78 1.48 1.76 1.62 1.63 1.61
3 1.41 1.18 1.41 1.20 1.31 1.20
4 1.00 1.00 1.00 1.00 1.00 (not listed)
Rev 2.42 2.42 2.42

November 30, 1962 dated FIA registration papers lists an alternate transmission.
XCO-270 alternate

The May 1965 issue of the SHELBY AMERICAN PERFORMANCE EQUIPMENT parts book has limited Cobra specific transmission information listed. The worst aspects of this book’s listing are:
1) almost no prototype, preproduction, SAI race team only, very early Cobra, custom ordered, or limited use parts are listed.
2) does not cover locally sourced parts and materials that shops besides Shelby Venice and Imperial Hwy used during car completions.
3) does not cover all the parts Shelby Imperial Hwy used to finish and or refit the last Cobra roadsters in most of 1965 and 1966
4) many small parts are not listed in any way.
5) some of the parts listed are service parts, i.e. production parts were no longer available so factory authorized replacement parts were listed.
So with the warning above, here is what is listed as SERVICE transmissions May 31, 1965.
C3AZ 7003- H Transmission, 4-Speed Stock Cobra Steel Borg/W Ford Ea 320.90 258.32
S1CS 7004 Transmission, 4-Speed Stock Cobra Aluminum AS2T/O-L Warner Gear Ea 323.13 258.50
S1CR 7005 Transmission, Pontiac Racing Gear 93, SK4516 AV Ford B/W Ea 319.80 223.86
S1CR 7006 Transmission, 4-Speed Aluminum Sebring Type Racing, SK4516 QK Ford B/W Ea 381.35 266.95
C2AZ 7039 C Transmission-Housing For Tail Shaft BWT-10-B7 Strong Competition Warner Gear Ea 36.63 35.64