L4701 holds a lot of hyd oil. I want to say around 9 gallons to fill it from empty (all 3 bolts drained), could be wrong.
Usually can drain about 5 gal of it out of the filter before it slows to the point where I've got to climb underneath and drain the 3 bolts. If you're quick enough, you can probably do it and lose less than a quart.
Somewhere-don't know if it was this site or what-there was someone who rigged a vacuum cleaner to the fill port and then removed the filter and lost no oil at all. I haven't tried it yet, takes less time to unscrew old filter and screw the new one on than it does to rig up the vacuum, plug it in, etc. Time is money when I'm doing this stuff for a living; and actually most folks that I am working for are telling me that it's more important to get stuff done quickly than it is to save a buck or two. Times have certainly changed I guess.
On a 4701, you'll have to put it on a large incline to get all the oil to slosh to one side, if you were to get it on that much incline it's entirely possible to lose hydraulic function, if it don't roll over in the process. Not worth taking the risk, IMO. Dont' forget on an HST tractor, you'll have two filters, the right side is the hydraulic filter and the left one is the HST filter.
how many people change the oil in their car by only putting a new filter on?