Metricnut,

Yes, a snap ring goes there. The parts breakdown of the starter actually shows two rings..one where you indicate, and another on the back, or starter side of the drive gear. Do you see a snap ring groove there as well?

They call these snap rings, but as I recall, they are circular rings, but not flat, and they don't have little ears like today's style does.

I don't think a conventional 'snap ring' will work. These are specific for this kind of application.

This ring sometimes ends up buried in a small recess in the end of the starter drive gear.

Stuart