Great story, thanks for sharing!Okay! I tried this suction trick with the assistance of my father-in-law yesterday! The good news is my 350 hour old hydraulic fluid looked great. I paid about $900 to my dealer for the 50 hour service, which is everything gets changed. It was a very light brown - looked like new engine oil. Guess those filters work pretty well! And as far as any "shearing of the molecules" might go from time in service usage or heating that could reduce its effectiveness, let me attest that stuff is slippery!
I know the hydraulic fluid color because it got all over the place.
To start my hydraulic fluid filter journey of discovery I took out the shop vac bag and the conical pleated filter. Put the shop vac on a step ladder on top of the bush hog to elevate it and used bungie cord to secure it . FIL (Ha! Father in Law, changing FILters, too bad his name isn't Phil) ensured the shop vac hose stayed put and also held the hose up so any fluid that might get sucked into it would have a lot of gravity to overcome to get into the shop vac. The shop vac hose fit perfectly into the hydraulic fluid fill port, and he didn't think it cracked the seal during my ensuing flail-ex, so he concluded in the future it would not need attending. Because it apparently fit so well I didn't use a funnel or duct tape.
I put a finger wipe of fresh oil on the rubber gaskets of both filters. Loosened the big system filter just a tad, then FIL started the shop vac. With suction going I began spinning off the filter. Before it was unthreaded it started dripping some around the edges and suddenly my hand was coated with fluid and super slippery. I did not think this through and have a basin of some kind to lay the old filter in so I just put it down on my concrete shop floor. Now fluid is dripping pretty good out of the filter attachment point - the shop vac is not holding it all back. I tried to pick up the new filter but it squirted away towards the bush hog and FIL. I yelled for him to kick it back towards me, which he did. Then somehow with my oil coated hand I picked it up (it is pretty wide) and spun it on. About two quarts lost.
The hydrostatic transmission filter I noted from print on its side is supposed to be changed every 200 hours. Well, okay, so that went 350 hours too. With the shop vac going it lost very little fluid - maybe half a cup.
Did the suction trick work? I'm convinced it helped. I think without it holding back full flow during my keystone cop routine under the tractor instead of two quarts I'd probably have lost two of the eleven gallons.
My progress towards "Country Man Certification" took one step forward for attempting this, but unfortunately two steps backwards for the preventable buffoonery I demonstrated!