not sure on a 3910 but 4630 just drive the tractor down into a small ditch. So the tail end will be up higher then should be 4 bolt holding a fange containing the seal. also there might be a pto safty shield to take off. Just DONT pull the pto shaft out. Should take 30 minutes. remenber do not take the pto shaft out. the seal is connected to the frange.then rebolt everything and recheck hyd level. good luck