I should mention that I had this same issue on my 98 LS400 and it was due to warping the pan while taking it off the transmission. Those pans are really stuck fast and when you pry to get it off, you will inevitably bend the pan on an edge, if ever so slightly. So, I cleaned the outside of the pan and let the car sit overnight. Next day, I pinned down the location of the leak and used a wide, flat blunt punch and hammer to peen the edge of the pan back into shape in the offending area. It worked