Speedometer Driven Gear

[DealsGapCobra]

I hope someone here can help my with my problem. I would like to replace my driven gear to calibrate my speedometer but don't know what part is correct. I have ordered a Ford part (shown on the right) and my original is on the left. The numbers are the approximate outside diameters of both gears so the new one is significantly smaller at 0.778" vs 0.850". Any ideas?

[Dan Case]

I can only report what was in the 1965 Shelby American parts list. The last time I replaced one in a Cobra was in the mid-1980s.

Driven Gears (installed on speedometer cable) Group 17271
Driven gears were selected by gear count depending on differential gear ratios and the diameters of original equipment tires.  Cobras street and race had variables in deferential gearing and tire diameters 1962-64 (even "1965" Cobras were built with 1964 model year differentials and tires).  Part numbers listed in the May 31, 1965 Shelby American service parts book include:

COAA-17271-A      17 tooth Nylon
COAA-17271-H      21 tooth Nylon
COAA-17271-J        18 tooth Nylon
COAA-17271-K        19 tooth Nylon
COAA-17271-N            20 tooth Nylon

[68blk500c]

Look closely to see if the teeth # is cast into the plastic in tiny font?
Sometimes it is.

I seem to recall the color coding corresponding to the teeth and Ford # is listed in the Ford MPC and/or assembly manual?

[Road Reptile]

Hi,
We need to clarify if this car still has a Borg Warner T-10 or possibly a Top loader was installed. Start with the simple. Casting numbers will tell what it is. Hope this helps.
R.R.

[DealsGapCobra]

Thank you for the feedback. I was able to get under the car yesterday and get this photo of the casting numbers on the T-10. It has a build date in May 1963. I didn't notice any other numbers.

[Road Reptile]

Hi Again,
Looks like Green sales co. In Ohio has the COAA 17271 A & K gears so if a 17 or 19 tooth would be correct I would call them and get an o.d. measurement. Then you need to calculate the correct part for your car. How many teeth on the gear pictured? How inaccurate is your speedo? Did you change rear end ratio or rear tire size?
R.R.