The engine will free rev OK, and it also accelerates on flat ground and the engine speed comes up with the forward or reverse speed.
On any hill, it won't rev up, and won't climb.
It is a shuttle type automatic transmission, forward and reverse on a column lever.
This is a project with deferred maintenance we just acquired.
It starts and runs smoothly, all functions are good except it needs a service brake overhaul.
My first suspects are a gummed up vaporizer or carb, possibly a timing issue.
The fluids are very clean and no leaks.