Dear Star Tech , thank you so much for a quick answer to a question I’ve been searching for hours the last 2 days !! My model does have the exterior reservoir tank. My mower works ok until it gets hot ( running for over an hour) then gets where it looses power to turn or go at speed. The mower is about 5 years old and hasn’t been trans serviced ( my bad). The fluid does look dirty. I have watched lots of videos and am familiar with how to do the hydro oil and filter change. Been a maintenance man for 45 years so I am somewhat mechanically inclined but this computer stuff drives me crazy with information overload!! Anyway thanks and have a great day ! I’m hoping this will help my trans last a while longer !!