I personnally have always used auto transmission fluid. Some disagree. See this thread where carl mentions flashpoint of ATF and power sterring fluid.

http://canadianponcho.activeboard.com/t52841083/power-steering-fluid-is-safer-than-automatic-transmission-fl/

Well, I'm sure there are guys on here that have more knowledge than I do but this is my experience.  I worked for about 4 years at the last remaining GM plant that manufactured the steering gears, pumps and even power steering hoses.  At that time I believe the primary use of these units were service parts and trucks.  The remainder of our plant locations were building rack and pinion assemblies and half shafts for front wheel drive.  The complex was for years and years know as Saginaw Steering Gear.  During my tenure we were known as Saginaw Division of GM, Saginaw Steering Systems and finally Delphi Steering Systems.

In 1990 I asked the guys in the plant to rebuild the power steering gear on my 1969 Nova SS I had restored in 1985.  I got the rebuilt pump back just prior to leaving for a Super Chevy Show in Atlanta, Georgia.  The guys were nice enough to include a new set of power steering hoses so I installed everything, put the car on my trailer and headed for Atlanta about 1200 miles away.  Upon unloading the car and driving it around the parking lot, I found I had a power steering pump leak.  Long story short, I spent an entire day trying to find the leak.  When I could not find it, I drove the car into a show on Sat. and then drove it 30 miles or so to the Super Chevy Show on Sun. with the belt removed from the pump (manual steering).  During the day of exploring for the leak, I read all the original literature I had and made a couple calls to sources back home for advice.  I was told to use Type F ATF which at the time was used by Ford for all their automatic trans.  I bought a couple quarts, not knowing now much was going to end up on the ground.

When I returned home to Michigan, I investigated all the parts a little closer than I could in the parking lot of the Marriott hotel in Atlanta.  My new power steering hose on the pressure side had been built with a taller nut than the threads on my gear.  Therefore when I tightened the hose 100% on the top of the gear, the flared fitting on the end of the hose was not entirely seated on the fitting.  I then machined about 3/8" off the nut and it worked perfect.

Bottom line, I would use Type F ATF if it is available.  As a result of the above experience, the guys in the shop gave me a handfull of brass "compression nuts" used in the fittings on the top of GM gears.  I still have them and have never disassembled a gear.  Prior to finding the leak, they gave these to me in case one was cracked on my gear and causing the leak.

Sorry for the lengthy post but at my age, I enjoy sharing my knowledge and experiences with anyone listening.  

I appreciate the info from Saginaw as I always use Type F !!

Thanks
Randy

Okay - So 2 new entries on this now. Thanks GLHS60 and 427carl. At least all of you responding agree on using ATF - as opposed to PSF in the mid-sixties GM power steering systems. Now though, it seems there are 3 posts suggesting ATF Type F, and one suggesting Dexron as a few others have done off-site. I'm not about to argue with Saginaw about the right fluid to fill my Saginaw system with. What bothers though me is the variance in the answers to the question across the web. From what I've read, original Dexron was apparently introduced by GM in '68, it turned out not to be the heavenly fluid it was meant to be, was replaced by Dexron II, then later Dexron III. All of these Dexron versions are supposed to be backward compatible. So I guess the new question should be :

"Type F Users & Dexron Equivalent Users Alike... Speak Out Together, Ya'll : Who's Had No Steering Pump Problems For Years On End Using Your Chosen Juice ? "

Finally - a vote for PSF. Thanks, Carl. There's one reply to the new question. ( I'm 59 myself, btw, but I've never had a 51-year-old Beaumont before ).

Yup. ATF lights up nicely. I've been incinerating all the damned used diapers I've had to wrap around that old pump for the last 6 months just to drive it without spraying the stuff in a circle pattern all over under my hood.

-- Edited by Tenrag on Saturday 16th of April 2016 12:29:58 AM