Power steering fluid replacement

Can ATF be used as a power steering replacement or as a top-up? I'm thinking the ATF might be a little thicker to reduce some small leaks when the ps fluid is hot.

That's what was used for years. Auto power steering,tractor hyd oil and power steering. I have used 10-40 motor oil in a pinch.

Ran 15w40 in our 9700 9600 and 8700 Ford. The Ford
mechanic said to because if one of the internal seals fail ps
fluid dumps into the crank case

In what? We are lost without at least a make and model of machine.

I use engine oil in my semi's so if a seal goes out the oil will not hurt anything in the engine. Been doing that since 1990's so over 20 years and a couple million miles total with no issues.

In/On what?? In a car or truck yes. In many of the older Ford tractor yes and say you have a 801/ series ford the owners manual calls for Type F ATF

Used to only use ATF as Power steering fluid. Then got to reading the service manual on one of my Dodge pickups and it specifically said to NOT use ATF in a Chrysler power steering system. The service manual states that the ATF would effect the seals. So I looked at what I usually kept for fluids. I tried 15w40 Motor oil, HYGuard hydraulic oil, Low Viscosity HYGuard and just regular 10W motor oil What I found that worked the best in the Dodge pickups was the Low Viscosity Hyguard. The motor oils and the regular HYGuard did not work very well in the winter.

Sign that the manual might have been correct is that I stopped having to seals issues on the Dodge steering boxes. Prior to this I would have to replace them about once each year. Now it is maybe every 3-4 years.

If you look at Power steering fluid specs. It does not have near the additives of ATF. So some of them Might effect steering systems. Some Ford systems recommend ATF so it all depends.

Power steering is simply a hydraulic system. About any oil will work. However, there could be issues with viscosity, compatibility with seals, or issues with internal components like spool valves. Manufacturer's recommendation is the only sure way to resolve those potential issues.

This would be an 1850 and a 570 Cockshutt.

The owners manual for my 9000 Ford says plain old hydraulic oil. I can see that engine oil makes good sense though.

Original type "A" trans fluid was 20wt non dergent oil with a red dye. It was used in auto trans and power steering applications. Then the next generation fluid had additives added, for oxidation and friction modifiers. Delco spec had more friction modifiers than the ford spec, so there where two types of oil at that time. Also around that time, sperm whale oil was used as it had better viscosity control than 20wt crude. IIRC around '74? the sperm whale oil was outlawed and replaced with a modern multi viscosity oil. As by then oil had improved a 100 fold and could provide better characteristics.

HD motor oils can "super clean" a power steering system and by cleaning, cause worn seals to leak. However if the seals are already leaking, into the crank case, then motor oil is usually preferred to reduce contamination of the hd engine oil with light duty hydraulic oil.

Lots of new hydraulic equipment is now calling for hydraulic oil with "anti-wear" additives so the line between hd motor oils and hydraulic fluids has been blurred. Also more pressure, higher flow rates, higher heat in hydraulic shifting applications have called for "synthetic base" hydraulic fluids further blurring the line between the high end motor oils and high end hydraulic fluids.

Old power steering systems ran 300 lbs of pressure, where 2800lbs and more are being run in some combination systems today.

Some PS units use PS fluid, others ATF, others hydraulic oil. Equipment manuals specify which. My take is that you are looking at basically a 20w oil for
cold weather so 10w-30 is the viscosity with seal swelling, antifoaming additives.

Mercury Marine says in their service manuals, look at what's in your system. If clear us PS fluid, if red, use ATF. If you are running the same part
number equipment with 2 different fluids, it must not make all that much difference. A '88 Ford 3910 I just bought specifies the same fluid used in the
trans/hyd/diff.....Ford 134 A,B....JD 303.

My Subaru specifies ATF for the power steering.