Disc orientation does matter. You see how the holes look like they are “cushioned” on one side more than the other? You want that cushioning to be oriented to accept the shock of the driveshaft decelerating.

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Current fleet
2006 E320 CDI
1992 300D - 5speed manual swapped

former members
1984 300D "Blues Mobile"

1978 300CD "El Toro"