Hobart a-200. My wifes mixer does not have first gear unless it is under a load then it will

Question

My wifes mixer does not have first gear unless it is under a load then it will engage in gear but does not have the same power it use too ! , Can you help ! My local hobart dealer is a **** and only wants to sell new ones and told my wife that she had no business with this mixer for her wedding cake business ? ! I am a equipment tech by trade so if i know what to do and where to get parts i think i can do the repair thanks chris