While using the 644 this evening to move some snow I had the misfortune of hearing the dreaded "POP" from the rear end that others have mentioned from time to time-sure enough oil was running out of a hole in the rear end housing. I was planning on rebuilding the whole tractor eventually and I guess now is as good a time as any. I will be starting a tear down on the rear end tomorrow and would appreciate any advice I can get as to what to look for while tearing down and what I should be looking for when taking off the top cover. I have all of the original parts books and service manuals for this tractor BUT hands on advice to Me is invaluable. I would also like the names of any trusted parts outlets You may have handy. Thank You for Your help. The old girl may have gone down with the sun this evening but She will rise with the sun again another day. (sorry for the poor quality picture)