Most likely its the rear main seal retainer. The retainer is what holds the seal in and the bottom of the retainer buts up with the upper oil pan. This is where the my leak was but I didn't know about the retainer. I droped the tranny and replaced the seal without the retainer and it still leaked. Dropped the tranny again and this time pulled the retainer and found that it was leaking there. Could of just dropped the two oil pans and sealed them.