Because of this thread, I really paid attention today, while I was out on my case skidsteer, doing farm chores. My gauge is metric, so that’s why I did the conversion from 160-175⁰F into Centigrade, was for myself. I do know that my hydraulics work better and better, as the hydraulic oil heats up. When running some attachments that use a lot of hydraulic power, such as a trencher, snowblower, auger, etc. I've seen the hydraulics oil reach into the low 80s C, and its still in the green on the gauge. My gauge is in the yellow when its cold, and then once up to 46 C or 115 F, it finally shows it in the green. The green continues until its at 85 C or 185 F. At 86 C or 187 F the gauge shows it in the yellow, and the yellow continues up to 99 C or 210 F, where it then shows it as being in the red.
So since this is about being in the range of 71 to 79 C, I was just curious is all, as to why the original poster felt that was too hot, is all. I'm often worried about pushing any and all, of my equipment too hard, when the hydraulic fluid hasn't sufficiently warmed up. Same with engines, transmissions, differentials, etc. I tend to baby my stuff, until all fluids are warmed up, and that goes so far as frequently taping cardboard partially over oil coolers. Right now it's been fairly warm weather here, today it was 10 C or about 50 F outside, not too bad for March 4th where I live, so I have the cardboard removed from my equipment, including tractors, even my airplanes. But I tend to cover them somewhat when its colder out, even blocking the radiator ram air grill on my ATVs, to try and get them to warm up more, as running too cold, is actually hard on stuff. I ride my Can Am ATV almost every day, its how I get around on the ranch, or in the bush when logging. On the digital dash, the display can be changed to show 1 primary thing, and a few secondary items. I leave it set to water temperature, as the primary thing shown, and never get hard into the throttle until its at a minimum of 85 C or 185 F. Maybe I worry too much, I don't know, but I do like stuff warmed up.
Tomorrow I plan to fly my personal plane, and will still have its engine oil cooler, partially blocked off, despite the temps being relatively warm outside. On cold winter days, its not uncommon for me to fly with it 3/4 blocked off, as my planes engine is air, and oil cooled, not water cooled. Its very hard on the planes engine, if the oil cannot warm up. I'll pull it out of its heated hangar, and fire it up, let it run until the oil temps into the green, before applying take off power. If on my flight down to kamloops, the oil temps not running in at least the middle of the green area on the gauge, I'll block off more of its oil cooler, before I fly back. I prefer it to be 2/3 - 3/4 of the way up into the green, but can live with at least half way.
.There are numerous Deere / Hitachi hydraulic pump “conversion kit“ install threads here mostly dealing with poor machine performance after installs. Good to hear you have some success !