Inspection of a 904 torqueflite

glhx said
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These have the same part number.

The taller one has teeth .0855
The shorter teeth. .0790

76 was the first year for the 4 forward clutch. The other one sitting next to it is a 67 with 3 forward clutch and shorter teeth for less frictions.

The teeth on the 76 are the same as the 999. Because the 999 has a 4 forward clutch. But the 999 is a 5” gear and the 904 is 4.5”

The diameter difference is because one is a 2:45 1st gear and the larger is a 2:74 1st gear. All the low 1st gear sets that I have seen use the longer splines because the low gear set models were all 4 clutch as far as I know.