This is the rubber plug on the bottom of your bell housing that give's you access to your torque converter drain plug...

 

It might be a futile effort....I was so accustomed to HAVING a drain plug on the TC that when I pulled the inspection plug on y 94' E4OD and went to drain it (after buying 4 gallons of mercon) lo and behold there wasn't a drain plug! After bumpig the starter and no plug in the hole, I pulled the inspection cover (that's where they were on the old AOD's) and still nothing. What a waste of time that was!