Topic: GT350 4 speed speedo gears

[Bossbill]

The SVO add/deletes do not mention the speedo drive and driven gears.
And the assy manual chart only goes up to 3.5 rear axle gears.

According to https://www.lucasclassictires.com/E70-15-Goodyear-SWT-350-Small-Letter-67-Shelby-CC7EX.htm the original tire is 26.73" in diameter.

According to the SAACForum the 68  GT350 (yes, 68 is all I could find) uses
the C2DA-17271-H with 20 teeth (driven). Same basic drive train, same tires, same rear axle ratio (3.89 both cases).

Running this through a speedo gear calculator I get a calculated 20.55 tooth driven with a 7 tooth drive. Moving to what I found in the transmission is a rose or tan colored 6 tooth drive which works out to a 17.61 tooth driven (not 20).

I need a left hand rotation driven so this works out to be a  20 or 21 tooth driven on a 7 tooth drive or 18 tooth driven on a 6 tooth drive.

What did these come with so I can get my order in and finish up the trans build?

[Bossbill]

Scott's 428 CJ calculator offers this result based on a Goodyear 500, listed at 26.73" in diameter. The driven gear of 20 teeth matches the SAACForum result.

Tire diameter: 26.85 inches; tire circumference: 84.353 inches
Optimal driven/drive ratio: 2.922

Closest matching ratio (difference of 0.065): 2.857
Driven gear: 20 teeth, C1DD-17271-A (Black) or C2DZ-17271-H (Blue)
Drive gear: 7 teeth, C4DZ-17285-A (Black)

[Texas Swede]

As far as I know the original 1967 GT350 4 speed with 3.89 rear gear ratio had a 6 teeth drive gear and with original tires the driven gear
should have 18 teeth.
Texas Swede

[Bossbill]

Good data point Swede.
The 6 tooth drive in mine looks original. I think either would work, but knowing what others have is invaluable.

Thanks.