Troy Bilt Pony M# 13AN77KG011 Is the rear end an automatic and if not why does it slip in higher gears. Have replaced belts, checked tension, still slips and seems to be getting worse. What could be causing this?

Hi,
First would be did you use the OEM belts; #954-0241A and #954-04001A since they are custom in length? Other than that it is probably the result of binding in the Transmatic bracket(s) No it is not automatic.
Peace,
Clarke