The upper part attached to the transom is the upper hinge. I had 1 leaking and rebuilt both of mine after Bennett sent me the kits. Kit comes with the plastic clip which makes it much easier and safer. There's a pretty stout spring inside the actuator and a lot of ATF.
https://bennetttrimtabs.com/installM...rMar19-WEB.pdf
https://bennetttrimtabs.com/installM...akdown-WEB.pdf
https://bennetttrimtabs.com/installM...O-Ring-WEB.pdf