I believe you have to have high pressure oil flow for the "hi-power" selection to work. There is an additional oil pump in the transmission section (just behind the bell housing) that supplies the needed oil and pressure. There is a bulkhead fitting on the clutch side of the bell housing with a metal tube attached. The other end is connected to the oil control valve which is part of the input shaft bearing housing. There are a few things you can check because it sounds like you may not be producing oil pressure or dumping oil in the bell housing. You will have to split the tractor. Once split, loosen the nuts and remove the oil tubing. Next, make sure the tractor is in neutral as well as the PTO. Rotate both input shafts, in the proper direction, to see if any oil is pumped by the secondary oil pump. If not, consider rebuilding or replacing the secondary pump. Another thing to check is the "o-ring" on the oil control valve spool. A 10 cent piece of rubber will shut you down, if worn or damaged. The next text is to take a air blow off nozzle with a rubber cone tip and stick the rubber cone into the oil inlet fitting on the oil control valve. Apply air pressure in both multi-high power and low settings to see if any air escapes around and through both input shafts. If so, the snap rings will have to be replaced on the other side of the bell housing.
