bolens st120 hydrostatic?

hello i have a bolens st120 hydrostatic and will not go useing the fwd reverse pedal, it sounds like a belt slip but i do not think it is slipping, on my other ride on a rover the hydrostatic has a lever on a spring to engage / disengage the diff and the sound is very similar that when disengaged, is there a lever hiding some where on it, cheers.