I don't really recall when it started, but the right side just would not keep up with the left. The hydro belt is probably a year old and appears to be in good shape. The tensioner was replaced at the same time with the updated tensioner. The filter was changed in may. Anyway, I can turn the tracking adjustment knob on the right side and pick up forward speed to match the left. But by doing so I lose most of the right side reverse speed.