Upon further review the issue doesn't seem to be the brake cylinder as I mentioned but actually a rear axle seal leak. You need 2 seals (one for each side) and they're normally about $5/ea. Its a good time to replace bearings as well.
I have the parts but it will be a few weeks before I can do the work.
Be sure to order these seals sooner than later because most auto parts stores do not keep them on hand and they have to be ordered.
Updates upcoming when this project is complete.
