Which D is the overdrive on a 93 Chevy Caprice?

On a 1993 Chevy Caprice, the overdrive is engaged by the D position on the automatic transmission selector. There isn't a separate "OD" or "overdrive" position like some other vehicles; it's simply part of the "D" range. To disengage overdrive, you would typically use the 3 or L position (depending on the specific transmission).