I am looking for some guidance here regarding a GT-14 with little pulling power. The engine runs fine, fresh ATF w/filter, trans fluid level up to the full mark, tow valve is parallel with the frame w/ the long arm facing forward as per the manual. Hydraulic cylinder works and takes about 10 seconds to go full travel (this would seem to indicate that the charge pump is working). Tractor moves both forward and reverse, but has trouble going up a 10% grade w/o pulling anything, even at full throttle. I have no experience with hydrostatic drives, so I don't know what is normal operation. I have a repair manual for the Sundstrand Hydro, but descriptions for checking the pump pressure externally appear to be for a '74 and later and they look different than mine.
Any help appreciated.