My 1984 300D may be different. When the key was jamming during rotation, it turned out to not be due to the tumbler, but rather to a broken detent spring housing deeper in the key stalk. The broken parts were jamming the rotation. Had to pry off a staked steel plate to get in there. I have no spring detent, but the key never rotates on its own, and still better than those notorious GM ignition switches.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans