I have a friend with a 4WD L235. He recently replaced the hydraulic pump on it. At the time, he had also replaced the hydraulic filter, and found paper element loose in the filter. He says that the 3 point hitch works fine up and down, but the pump whines, like it is under load. Are there screens in the hydraulic system of that tractor? I'm thinking that perhaps he has debris on the screen/s, reducing the flow to the pump? Any ideas or experience?