Power steering fluid or ATF?

[Nothing Special]

As I'm wrapping up the hydroboost install on my Bronco I'm wondering if I should be filling the system with power steering fluid or ATF. I've been using power steering fluid, but I know that in the '90s Ford recommended ATF in the power steering system. If I were to switch, this would be a good time.

Any thoughts on which would be better to use?

And to flesh out what parts I have, I think it's a Bronco power steering pump, an F-100 steering gear box and a '95 GMC Safari (aka Chevy Astro) hydroboost.

 

[68rustbucket]

All my fords up to at least ‘03 f250 used ATF in the ps system. On my street rig I’ve been using it since 03. When I had my trail rig I used ps fluid in the hydro boost system, because that’s what PSC recommends.

 

[Broncobowsher]

I've filled power steering systems with 90wt gear oil before, field fix but it worked fine. My tractor ran a single fluid for the transmission and complete hydraulic system. It is amazing how little it cares what it is pumping.

With that said, I would tend to put in a fluid intended for the application. Power steering fluid typically has better anti-foaming properties at the higher pressures a power steering runs at. Power steering, 2,000 PSI, Automatic transmissions 200 PSI. For a top off, use what you have. Buying something specific for a fill, just run power steering fluid. ATF also has some strange friction modifiers that have no business in a standard gearbox. You don't have a wet clutch that you are trying to smoothly apply, so why are you wanting to run modifiers for that?

 

[Nothing Special]

.... With that said, I would tend to put in a fluid intended for the application....

I agree with that.

.... You don't have a wet clutch that you are trying to smoothly apply, so why are you wanting to run modifiers for that?

Because it IS the fluid intended for the application. At least in my '97 F-250 Ford says to run ATF in the power steering pump. And take this for what it's worth, but what I hear on a forum for that truck is that the Ford pumps whine a lot more if you don't run them with the recommended ATF. I know that Ford power steering pumps have always been known as whiny (hence the popularity of Saginaw swaps). So I'm wondering if ATF is a better choice in earlier Ford power steering systems as well.

 

[pcf_mark]

I ran ATF in my stock pump and it was squeaky. I switched to power steering fluid and it stoped squeaking. When I did my Explorer front dress conversion I just used the power steering fluid too.

 

[Broncobowsher]

I still use power steering fluid in a power steering system.

 

[Montoya]

Power Steering vs ATF Fluid

Jon

 

[Montoya]

Ford putting ATF fluid in from the factory shouldn't surprise anyone. I have a bunch of engineering friends who work for Ford and they purposely design parts to fail after the warranty period. I assume some bright guy figured out that ATF fluid will cause the pumps to fail after the warranty period and that if they only used one fluid it would save money (economy of scale).

One of my friends entire job is to tear down trucks that have exceeded the warranty period and find out how to make the parts that lasted fail. He says his boss always says "any part that isn't broken immediately after the warranty ends is over-engineered". They work in accounting.%)

 

[landshark99]

I would put a good quality Power Steering fluid in - the AC Delco Power steering fluid is some of the best out there for the price. Also if your pump whines this will quiet it down or eliminate the whine.

I didn't believe it when i was told and thought - snake oil! well it worked for me in three Broncos with a saginaw, stock ford and Ford Explorer pump - and now thats all i run.

I believe it has something to do with the addition of more frothing formula or something or other...

 

[73azbronco]

I'm using the swepco 715 with my PSC pump for warranty, anyone know offhand the comparable street version I can use say I'm in the middle of nowhere needing some?

 

[ET]

I have psc pump and reservoir running napa ps fluid. I don’t drive much except around the block once/twice a week. Works fine in couple of years. Trying to make roundup in fall to test it.

Eugene

 

[Rustytruck]

atf for ford pump and power steering fluid for GM pumps. More important to add a real cooler especially for tight trail work.

 

[Nothing Special]

atf for ford pump and power steering fluid for GM pumps. More important to add a real cooler especially for tight trail work.

ATF even for an old Ford pump? Or was that something they went to later? I'm not sure what my pump is off of, but I'm thinking it's either a '70s F-series or an early Bronco. (My Bronco came with manual steering, the power steering was added later)

 

[bronconut73]

The power steering system is such a small volume I buy the most expensive/best shit i can find.

I think I am using RedLine in there right now.
Overpriced and likely much better than what I really need, but again it such a small volume, why not get the best stuff you can.
Power steering systems operate under much higher pressure than an auto tranny so clearly the fluids are developed for quite different environments. Trannys make way more heat. Its just two pretty different working environments.

So again, why not splurge on the good stuff made to operate under the expected conditions.

I noticed an improvement from installing an aftermarket cooler too. But it was immediate improvement. From the first turn of the wheel before any heat could be built up. Perhaps the additional volume or perhaps some remaining air got removed.....perhaps the way the lines are ran I am not frothing the fluid as much but my power steering system is better than it has ever been.....stock/junk yard Explorer ps pump set up with a large cooler and high dollar ps fluid is the best I have had for my eb after 37 years of eb ownership.
And yes I had a Saginaw in the past. This Explorer system with big cooler and fancy fluid is smoother and lighter to the touch.