My problem is with the tractor gradually losing speed, not the engine, the transmission, until almost no response. I have changed the filter and verified correct hydrostatic fluid level. Trying to troubleshoot, I did discover that if I move the up/down deck handle all the way, I instantly get full power back. To mow I would have to hold the handle forward. I know something is not right and need to correct it before I cause serious damage. I appreciate any help you can give.