Mine does not have one,  Any other way to drain it? possibly by removing the lower tailshaft bolt? Suction gun or vacuum pump seems to be my only option. If I had noticed this before I had it rebuilt it would have been simple to drill the bottom of the case and tap it for a 3/4" pipe plug. The boss is cast in the case but it is not been drilled and tapped. Never saw a transmission without a drain plug. Wonder what genius engineer came up with that bright idea.