Nice looking 1641.
You can get at the drive shaft fitting by removing the tunnel cover and the side panels and while you have the side panel off you should be able to get at the fitting on the steering box. Recommend you also change the oil and filter for the hydro unless it has been done recently. This link will take you to a bunch of stuff I've done on the Cyclops tractors. Should keep you busy for a couple minutes.
http://www.onlycubcadets.net/forum/s...ad.php?t=33244