These weren't meant to be serviced per say. If there are no signs of leakage, I personally don't worry about them. There is an oil plug/ drain on the top near the front. It takes a pint of 80w90 from empty, so if one comes apart- you clean it up and put that in and you are done. If you want to service it, you have to remove the transmission, clean it up, remove the plug and invert it. gear oil runs nice and slow too .