The vent goes up, not to the basement. If the vents are galv. steel I cant tell you how many I have worked on that plug with rust and debris over the years. If the drains are galv. steel they are likely plugged so the id. is about as round as your little finger.
Replace all the galv. pipe with plastic and be sure to check where the drain runs into the stack that it is open also as they clog there just as bad as the pipe.