The 21130692 is the upper gear set for a DPS-M drive that is used on
gears with a ratio of 1.68:1, 1.78:1 and 1.95. (The lower unit of the
drive is what determines what ratio the whole drive is.)
The 21130693 is the upper gear set for a DPS-M drive that has a ratio
of 2.32:1 only.
The 2.32:1 gear set is sort of a rare gear ratio. The 2.32:1 DPS-M drive ratio was usually used only on small gas 4.3 engines or early D3-140 or some D3-160 diesels.
The vast majority of DPS-M drives were either 1.95:1 (probaby 65%) and for the larger horsepower engines 1.68:1 and 1.78:1 ratios (probably 25%).
The way it works is that there are two different upper gears that cover
all the ratios combined with three lower units that determine what
the entire gear ratio.