Thats where the vent is, as to why oil is coming out it could be a number of things such as the ones suggested or improper building, case stretch, oil quality, etc. Whats the age of the oil and type (some oil is starting to suck these days)? Condition of the trans? How hard do you run it? All in all it's probably not worth it to worry about it unless you are drag racing, just keep an eye on it.
i found some lube at rural king its a g5 type for gear boxs, i bought trans 2 years ago used , it shifts flawless, and sync are in great shape, i dont run run the car hard its just a cruiser anymore quit racing in 2013 thanks for the info