I am not positive but the PTO is probably not supposed to be filled with 90 weight. I think it is to be filled with transmission/hydraulic oil which is for sure not just "plain ole 90weight". Any how, look to the right front of the gear shift lever, the dip stick / fill plug should be there. It should be very similar if not the same as my 4025. Be careful what you pour in, it could make you pour in a bunch of cash behind it.