"Dexron type Power Steering fluid" (1 Viewer)

[toyotaboy80]

My box and fluid reservoir leak so I found some bone dry on the outside replacements at a junk yard.

The reservoir is out of an '86 2wd truck and says "use Dexron type Power Steering fluid" on the cap
And the box is out of a '90 4runner.

Both trucks had a similar oil in them... atf like smell in them and both were transparent/copper/clear-ish. The 4runner I pulled the box out of was pretty low KM and safe to say was probably the untouched OEM fluid in the box. Guessing it doesnt leak because of not being molested with random fluids. And I'm assuming the 86 truck and 90 4runner are speccing the same fluid...

So, what is a "Dexron type Power Steering fluid"

Is that just straight up any Dexron ATF? Or is there a secret Toyota "power steering" fluid that has Dex in it?

For the people who have a leak free PS system, what fluid are you using?

 

[gnob]

Dex atf is the norm.
I use amsoil tractor hydraulic 5w30.

 

[pappy]

Is that just straight up any Dexron ATF?

Yes.

 

[GRM]

I always use Sta-Lube Red Power steering fluid. It has a much higher flashpoint than atf, and I’ve found it does not boil over nearly as easily.

Part# SL2631

Edit: this fluid is designed as a replacement for vehicles that call out ATF, including Toyota. This is not standard power steering fluid.

 

[toyotaboy80]

thanks for the replies.

Some reading says Toyota called for Dex II/III. But, that's no longer sold and has been replaced by Dex VI at this point. Based on what you're running(gnob and GRM), I guess it's safe to say that really the steering system just needs a fluid that is capable of handling heat and acting as a hydraulic fluid? SO, that would mean just about any fluid that meets the temperature/hydraulic demand and is seal safe should do the trick in a power steering application.

Am I on the right train of thought?

What fluid is to be avoided? I.E which ones are going to cause the seals to fail? I've seen some mention to avoid using "power steering" fluid because it will create a leaker... but if it's designed for heat and the hydraulic action of a PS system and common seals, why shouldn't it be used? Red herring?

 

[old87yota]

The "power steering fluid" for these trucks is indeed Automatic Transmission Fluid.

This is what I would use: Toyota Dexron II and III Replacement Fluid

It is Toyota's replacement for Dexron types II and III. It leaves no question about compatibility.

You can shop around to find the best price, or go to your local dealer.

Photo source: By Hymn62 - Own work, CC BY-SA 4.0, File:Toyota Dexron-III ATF.jpg - Wikimedia Commons

 

[KLF]

Do NOT use off the shelf Power Steering Fluid. It will ruin the bearing and the vanes in the pump.

 

[ntsqd]

What KLF said!

If you research Dex IV I think that you'll find that it is considered safe to use in Dex II/III applications. The stuff sold as "Power steering fluid" in the US is different in composition from Dexron ATF. A fair number of domestic truck drivers use either interchangeably, but do not do this in a Toyota system.

 

[toyotaboy80]

Do NOT use off the shelf Power Steering Fluid. It will ruin the bearing and the vanes in the pump.

What KLF said!

If you research Dex IV I think that you'll find that it is considered safe to use in Dex II/III applications. The stuff sold as "Power steering fluid" in the US is different in composition from Dexron ATF. A fair number of domestic truck drivers use either interchangeably, but do not do this in a Toyota system.

From what I've read dex vi is pretty well the same in property as dex iii except for its a thinner oil. From a pressure stand point it would produce less steering assist due to being able to flow better. Not sure if it'd still be thick enough for proper pump lube/protection in the long run.

At shear value, their viscositys are pretty well the same. Not sure how often the PS system puts an oil in shear but if it is quite often then Id bet thered be no appreciable steering loss or additional wear in the pump.

I picked up a bottle of AC delco Dex vi for top ups in the meantime until I can get around to swapping in the new box. On the back of the bottle it says it is also a suitable oil for dex ii/iii application.

At this point might just run the ac delco dex vi when I swap the new box in or if I convince myself that the thinner viscosity is an issue I'll try and source some of the stalube or OE toyota oil.

 

[ntsqd]

Now if I could just figure out what to use in a system with a Saginaw pump, Hydro-Boost, and the Toyota steering box. I'm thinking Dexron in favor of the box.

 

[toyotaboy80]

The more I think about it the less it matters "exactly" what oil goes in the system as long as it protects the pump, handles heat, acts as a hydraulic fluid, and is seal safe.

Really the system is just a pump spun by the engine and a spool valve in the box(and in the ram assist application theres a double actuated ram).... just need a seal safe oil that is capable of handling heat(aka acting as a hydraulic oil) and provides protection for the pump when spinning at xxxxRPM....

Theoretically all the box is doing when the input shaft is turned left or right is allowing the high pressure oil from the pump to hydraulically assist the output shaft. All this is spinning extremely slow relative to the pump and likely sees very little protection from any fluid used.

Likewise all the ram sees is high pressure oil and forces the piston in an appropriate direction.

ATF when used in an auto trans hydraulically actuates and protects from high speed spinning wear, and handles temperature reasonably well until it straight up gets too hot... by then, most fluids will have trouble keeping up with heat.

Seems reasonable why ATF gets used and not a totally reinvent the wheel renamed fluid doing the same thing. Auto manuf. Prob just said run dex i..then ii... then iii due to its readily available-ness and meets the demands. And because it was a credible/licensed standard of oil to be used, not just a "slap some ATF in there". I could take a jug of milk and label it ATF. But I cant label it Dexron ATF because it doesnt pass a certain quality to do a job that an auto trans needs. Probably just so happens dex atf was selected by Toyota at the time.

And just so happens some years later the number changed from a i to a vi... theoretically its still just a dexron atf and vi should be better than any # before it, but its still a standardized ATF.

Its likely you could run ANY atf produced by a reputable manufacture or straight tractor hydraulic fluid. Excavators and graters use pumps and rams and spool valves all day long without failure....just a simple hydraulic fluid.

But...without totally getting into the specs of every single fluid and their capabilities, strengths, and weaknesses... its easy enough to just fire Dex VI in there and call it a day unless you need something capable of handling higher heat before boil over(as per already mentioned)

 

[ntsqd]

You hit the two points that I've felt were important for some time, mechanical and seal compatibility. Mechanical is fairly easy since pretty much any fluid that can maintain a protective film in the worst case situation will work in this system. Seal compatibility may not be so easy. ATF's usually have chemical components in them to keep the seals from hardening under the heat, PSF does not appear to. A seal made from a PSF friendly polymer may not really like having ATF around it, and vice versa, a seal needing that property that ATF has may not behave well with PSF.