Any ideas on this one?

I changed my T5 trans fluid for the first time (at least since I've owned the car). No problems, I took out the fill/drain plugs, dropped the old fluid (it was ATF), replaced the drain, then used a little pump I bought for $6 at Advance Auto and refilled with ATF as stated in my shop guide, about 3.5 qts until it just barely dribbled back out the hole, then tightened up the fill plug. No problem. The car is currently on jack stands as I do other work ... I come out a day later and there's a couple of drips right under mid-transmission, where the tailshaft housing gasket is. What gives? There were NO leaks before, and the drain/fill plugs are not loose/under tightened. Why would I have a leak now? Is the new ATF a bit thinner than the old stuff, causing a small leak through old gasket? This is by no means a major leak, probably a couple drops during the day, but it still irritates me.

Thanks all ...

 

Maybe overflow?