Happy 4th y'all

I spent the day adjusting the valves on my 83 300D. Then I did a diesel purge and changed the fuel filter. After a 15 minute test drive, I returned home and saw a growing puddle running down the drive. It seems to be tranny fluid and its coming from the grate looking thing at the bottom of the bellhousing. Any thoughts on a cause?

Why so sudden? Tranny had been perfect up till now. The car has around 140,000 on it.