Here's the schematic with the notched pin. I should have looked for it earlier. There's a set screw #41 that goes into the notch.


The schematic for the plain pin comes up the same, showing the notched pin. I now imagine either pin can be used with any matching shifter in the M series trans. The set screw in the notch would act as a better retainer, less likely to loosen and let the pin work loose. Also, the metal used with the notched pin looks different in pictures, perhaps harder to lessen wear, the set screw no longer grabbing as well into harder metal, hence the notch to prevent it all working loose. I was starting to think of thread locker, but then whoa, not with a set screw, you'd never get it out.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now