Fluid for steering pump

Personally and technically, I wouldn't use ATF because of it's friction modifier package. Power steering oil is fine but it costs more in bulk, and if you look at the ingredients label on power steering oil guess what you'll see…

On my 304 the PS pump looks just like the hydraulic pump for the lift box, so I stick with hydraulic fluid.  These tractors use a straight pump and cylinder system for steering, unlike a car that uses a high displacement pump and a recirculating  ball steering system. 

A good quality hydraulic oil should be what you need. These Jinma steering systems are straight hydraulic – using a hydraulic cylinder rod movement to turn a steering knuckle and hence front wheels.

Depending on where you are would influence the oil choice. I live in an area that frequently gets -30 F temperatures in the winter. For me the hydraulic oil I use is AW32 – the AW46 is too thick at these temperatures. There is a noticeable difference between the two oils at start up operation.

HTH

mariner