MF35 hydraulic oil

The previous owner said he had within the last year or so replaced it with "expensive" fluid he bought from the MF dealer. He knew enough to not put GL4/5 in it, but I'm not sure exactly what it was. The hydraulics works fine, except when lifting something heavy (6 foot box blade or brush hog) the lift is a little jerky. The fluid seems pretty thick (thicker than the GL1 I've used in other tractors) and it has small air bubbles in it (on the dipstick). The color is slightly milky, but it looks more like air than water. I thought the oil might be Permatran 3, but from what I've read it should be thinner than GL1.

I'm planning to put some 90 weight GL1 in it this weekend (and to flush with diesel in the process), but I'm not sure what to think about the bubbles. Could this just be due to the thick fluid, or would this indicate some other problem? I haven't yet removed an inspection plate to look inside since I don't have any gaskets, but I have some on order.

Thanks,
Shawn

I have the correct gl-1 90 wt mineral oil in my TO-35 trans/hyd system.

the old tractor was getting a little tired, everything worked properly, but lift system would no longer lift front of tractor off ground if I tried to pickup something too heavy for the tractor.

I poured 1 qt of Lucas oil stablizer in system.
Old girl works great now, lift will pick up front of tractor now just as it did years ago.

might be worth a try, cost about $9 bucks. If it does not help do not believe it will hurt anything. 1qt in 8 gals of oil.

I don't know what type of oil it had, but it was very thick and milky (almost gelled like brown turkey gravy). Fortunately though, I didn't find any rust or significant sludge. I flushed it with a few gallons of diesel, replaced the hydraulic filter and gaskets, and refilled with M1129A (Permatran III). The milkyness is now completely gone.

I really like this oil so far. It is thinner than the GL1 I've used in other tractors, the lift is more responsive, the shudder/jerky movement is gone, and the leak-down is not bad at all. I haven't tried lifting anything heavy enough to lift the tractor, but I'll try that maybe this weekend.

The shift lever boots both look pretty new, but the boot at the end of the big draft control spring is pretty much gone. I'm not sure if that would allow water into the system, but I'm guessing it might. I'm planning to keep the tractor either garaged or shedded, so hopefully I can keep it dry in any case.

Thanks,
Shawn