Can you substitute standard hydraulic fluid for ATF in an old Melroe Skidsteer?

[GlennsM444]

I have a 1964 Melroe Bobcat M444. The specs for hydraulic fluid call for ATF. I am replacing the hydraulic pump and I'm considering draining the fluid and flushing the entire system.
Has anyone ever substituted standard hydraulic fluid for ATF in these old machines?
the capacity for this machine is 15 gallons and standard hydraulic fluid costs about half of what Dex/Merc costs at Auto Zone.

 

[jerry]

Maybe if you use a thin hyd oil,I think aw32 is about the same as #10 motor oil. Too thick or slippery a oil would make the clutches slip a lot.

 

[jerry]

Maybe if you use a thin hyd oil,I think aw32 is about the same as #10 motor oil. Too thick or slippery a oil would make the clutches slip a lot.

Cold weather would be worse with thicker oil of course.