I've never seen a transfer case on a tractor, front driveline comes out of the rear half or transaxle on mine. The rear half on mine has multiple plugs for drains.
i have your exact same tractor and the "transfer case" is part of the rear axle/transmission/hydraulic oil. So, if you change one, you've effectively changed them all. Makes it easy.
Maybe I shouldn't have said transfer case.. I'm talking about the small right angle gearbox that powers the front driveshaft. I sort of figured it must be lubed by the main sump- I cannot find plugs on it to drain or fill.
