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Hello. I have a Cub Cadet Model 3225 that I have owned for about fifteen years. Over the past couple of years, the hydrostatic transmission has seemed to have gotten weaker and weaker when going uphill. It used to run great when I first started mowing and got progressively weaker as the day went on. So far, I have replaced the fluid and filter, added a hydraulic oil cooler, and I just replaced the geroter in the charge pump thinking that may be the problem. The old one, however, looked fine and there was no change in function. I replaced the o-rings and thin orange shim when I did the geroter, and made sure the new one was oriented properly. The power steering and lift both work fine. Today, it has gotten so bad I can no longer mow with it, as it will now not even pull the slightest bit of grade at all. I can hear squealing and feel a vibration when I push the travel pedal when trying to go uphill. I have checked the fluid, and it is full, although when I strain it to try and go uphill it becomes frothy.

Does anybody have an idea of what may be wrong and how I could fix it? I am fairly mechanically inclined, although I am not terribly familiar with hydrostatic transmissions. I appreciate any input or ideas.

Thanks,
Andy