I need info on how to drain and fill this hydro unit. I have gone to Eaton's web site and down loaded the schematic. I have read it backwards and forwards but no where do they mention how to drain and refill this drive pump. This pump has no filter and is used on Ferris SD36" and SD48"s. I talked to my Ferris dealer and without blasting them.........I'ld rather ruin these units myself than to pay some one to do it for me!! Any help would greatly be appreciated. Thank you!