On my buddies old Evo, he had a small hairline crack on his tranny that would weep oil. We drained the tranny, cleaned the area thorougly, and put a healthy dose of silicone all over the cracked area. Worked pretty well, but certainly not an ideal longterm fix.

If you had a large puddle of fluid, it sounds like more than a hairline crack to me. Seems like you got nothing to lose. Try out the JB weld and see what happens.