I had my gearbox go out- took it apart and found that a shaft had wallowed out a bearing causing the gear to break a couple teeth. Powergear would provide me with the parts I needed, they would sell me a new unit for about $800..... I searched around and found what I needed to repair it.
Get the part #'s off it and call Armondo @ 352-351-0759 .... it was about 3 years ago when I was at his place, but he literally had a room full of motors/gearboxes mostly used but also new stock he had bought from dealers that had gone out of business and he had super good prices