Hey, welcome to the forum! As you can tell by my name, I love these riding mowers and know them all like the back of my hand lol. Anyway, I'm assuming you have the manual version, not the hydro variant, correct? For the manual transmission I would try to find a leverage point and try to pry it off with a flathead screwdriver or a crowbar. If you have the hydro... You really shouldn't even be in there lol, bring it to a mechanic to do the job right. Maybe upload a picture?