Won't shift?
 

I just got an ATV that's been stored for a good long while. It's a John Deere Buck 500 Auto. The oil was crap, which i changed, but i didn't change the filter. It was the engine oil and transmission oil are the same thing. I charged up the battery and it starts up fine, but it won't shift from 1st gear. I've tried automatic and manual modes but it still won't shift. I drove it around for a while in 1st but still nothing. Anyone know what I can try next?