It uses lithium grease like mine, 90wt might work. Mine is an 845 GT model number 146S845H088 it has a High/low like his only difference is mine has 18.5 hp in it.
I belive you have to open it up or there is a small rubber seal on the top, you can take that out and fill it up, but you should drain the old grease out. I've never done it but I think I might give it a try.Thanks how do you put it to the tranny?