I have a SLTX1054VT with the hydrostatic drive. It started slowing down going up small inclines the last few times I used it. Now it won't even power through a turn. I checked the mower deck belt, fine. I checked the drive belt, fine. I have watched a few youtube videos on putting fluid into the hydrostatic transmission on other tractors, but I don't think this trans has any access or fill ports. I have read that they are sealed at the factory. Is there a way to fix this issue? Suggestions? Thank you in advance.