My ventrac 4200 that I purchased used has ran great up until yesterday. I was mowing on hills and all of the sudden it started losing the torque needed to climb. The engine sounded fine and it felt more like the hydraulic pump. It would move forward and reverse on flat ground but it struggled on hills. I took it to my garage and I did notice that the hyrdo reservoir was way past the cold mark normal mark almost to the top. I may have over filled it a couple of weeks ago. With that said does anyone have any ideas or suggestions. The local dealer here is great but they have a 3 week wait and I need my tractor sooner than that. He suggested I may have sheered a pin on the hydraulic pump? Also any suggestions on trouble shooting this issue would be appreciated? Help???