I have a S300g, 52 starting serial number, 2 speed. Left drive is extremely jerky with little power, right drive is better with more power. I have replaced both wear plates in hyd pump, and also replaced both relief valves on right and left side. Rotating groups appears excellent. I capped off drive motor hoses and stroked levers and had the same problem, I wonder if my hoses that control 2 speed are dumping my hyd pressure, due to a fault in my 2 speed valve. Or do I have a cracked section in my hyd pump! Any ideas?