904 question. Please help.

Got a quick question for you. A little history on my 904 behind my fairly mild 318, TF-2 kit, 3000 stall other than that it's stock. The problem that I have is that sometimes when I drive it hard it will piss tranny fluid out of the bellhousing/convertor area and make a big smoke show. I mean it pours out and I leaves a trail down the street then it will just stop leaking. It has only done this 2 times in 350 miles. This 904 came with my basket case dart when I bought it and it shifts great with no slipping at all. It does not leak a drop other than that. Is it leaking around the input seal or is there something else in that area that would leak like this? I replaced the input seal the last time that I had the motor out just because and made sure that I didn't damage the seal when I reinstalled the convertor. The convertor is new and is a Boss hog street bandit. Thanks in advance for your help.