ATF will work fine in cold weather. Some mfg recommend it for all weather types. AW32 and universal tractor hydraulic fluid are a couple other choices. There are some that use straight oil ( mineral oil) in various weights as well. I have been using AW32 for some 20 years in my splitter- course now days it's a Harbor Franken splitter.
Well today I made some progress ..
Got the new pump and coupler bolted on . I made a new safety shield to cover the motor shaft and coupler ...I don't have it bolted on yet though .
Took the valve apart and cleaned it to make sure there wasnt any metal in there . Everything looked good ..I got some measurements for new o-rings while I had it apart . My local suppliers didn't have the correct size so I just cleaned and put them back in . They didn't leak before so I'm hoping they are still ok to use .
I got the new cylinder bolted in place and the two supply lines connected to it . I ended up turning the rear cylinder line 180 with the bend down to make some room for the new filter . It looks better and should function just the same .
My new hydraulic tank should be done this week and then all thatis left is to connect the supply and return lines .
Once that's done I can extend the cylinder and weld the push plate to the end .
Here's some pics...