I had the same problem mine got to the point that it would not pull up the slightest hill, so I went into it and took out the center case, some people would call it the valve body, but anyway I'm a machinist by trade and I took the center case to work and resurfaced the mating surfaces on the center case and the spring loaded pumps or motor and pump, if those surfaces get scratched they will lose pressure and the tranny will stop pulling or pull slow. I just put it back together Sunday and tried it. It started out slow like it wasn't getting enough pressure, but I then bled the air from the pump by using the bypass valve and pressing forward then reverse several times. The tranny started pulling and doing better. As of now the tranny is pulling very strong. I also filled mine to the top, the book says 3.7 quarts, but I put 4.5 in mine 20W-50 motor oil and it works fine. The more I drive it the stronger it seems to get. When I broke it down I noticed that the parts I machined where ground, but I used an endmill and resurfaced mine like that. I believe that's why it’s getting stronger the more I run it. There is a difference in machining parts and grinding parts. Grinding seems to mate the surfaces better, but anyway machining the parts seems to work. If you need this job done give me a call my name is Maurice 910-384-4282. I think I can do it for you for $75.00 if you take the part out and send it to me. Call me and leave a message I will call you back and make sure you say it's about these Kubota hydro trannies.