727 transmission leak

Common places they leak are shift shaft seal, dipstick tube and shaft for rear band lever. If your sure its leaking on the front driver side I would replace the shift shaft seal and go from there. They are almost always bad if they have not been replaced recently. You can do it in the car but its tight. Last one I did on a lift and used a mirror to see what I was doing. Pop out the old seal with a screwdriver and installed with the special tool. You could probably find a suitable deep socket that would work instead of the special tool.