Fluid- 1977 John Deere 70 skid steer?

[dlbernau]

I am in the process of getting my dad's old 70 skid steer going and need to know what fluid it uses in the hydraulic system. My dad seemed to think it isn't hyguard but rather some type of car transmission flui. Any ideas anyone? TIA

 

[skidsteer.ca]

If it is red and thin then it would be Atf likely. Not sure if it matters if its dextron, type f etc.
It gets very pink if its old and has condensation or water contamination.
Skidsteer.ca