Being sealed mean they are not something normal operator should be doing as it takes a very environment to service these units.
You would need to remove each unit, remove the vent or fill plug after cleaning the exterior of the transaxle, and invert transaxle to drain all the fluid out. Filter screen seldom ever needs changing. But in order to change it you need to open the unit up and pull the center section out to the two check valve holding it in place.
Be careful removing the vent plug as currently HG has it as N/A. Glad I got three of them here for my customer repairs.
Adding a drain plug is something I got to look into on the unit I am rebuilding in a few weeks to see if it is possible without interference of the center section and filter.
These unit are refilled with SAE20W50 motor oil preferably Synthetic oil.
