I have a 1950 8N that has cotter keys coming out of the transmission case near the drain plug and another one in the crankcase. I drained a large quantity of oil from the crankcase and the transmission case so I don't think they leaked. I just would like to know what they are there for. I have another 1947 8N that does not have the keys. I tried to post a picture but I am technically challenged.

The holes are there to allow any oil that leaks from the rear main seal of the engine or input shaft of the transmission to drain. The cotter pins were put in the holes with the idea that they will jiggle within the hole preventing them from plugging.

Mark