I had the same problem. I replaced the dipstick tube o-ring and the pan gasket, since it seemed like it was coming from the right front corner of the pan. That didn't fix it. I had it to a transmission shop, and they replaced a few easy seals (speedo cable was one). But it kept leaking. They had it up on a lift, and had it running, but it didn't leak at all. They would come back the next day and there was a puddle on the floor.
They discovered that was a shaft at the left rear of the transmission that I believe runs horizontal and parallel to the tailshaft; its part of the reverse shift band connection. There is an o-ring seal on that shaft that leaked. Because of the location, it requires complete disassembly of the transmission to fix it. Over the winter, I tried drying and blowing all of the residual fluid out of the gap and cleaning as best I could, then I applied Blue Permatex sealant. That helped, but didn't fix it.
In the end, I threw in a bottle of lucas transmission sealer, and that seemed to have fixed the problem.
It also seems that the more I exercise it, the less leaks it has.
