I thin you're talking about the vent on top of the tube. You drain it by removing the cover. You fill it through a plug on the lower part of the pumpkin. To know if it's safety track (AKA posi), turn one wheel and if the other wheel turns in the same direction then it's a safety track and requires special oil or additive. If the other wheel turns the other direction then it an "open" read end and uses regular gear oil