Dexron vs Type F ATF in Power Steering

[giantsforever]

I have a 1988 Volvo 240 DL normally aspirated with power steering (ZF type). The manual calls for Type F. I'm wondering if I can use synthetic Dexron instead, because I can't find synthetic Type F and have lots of synthetic Dexron?

I read an anecdote about the power steering leaking a while after switching from Type F to Dexron, but I don't understand how that can happen?

Also, what's the difference between the two types of ATF?

Thanks!

 

[Astro14]

I used Type F (conventional) in my old 240 for a long time. Never had an issue. In the Bay Area (mild climate) I would just go Type F and not worry about needing a synthetic.

 

[CharBaby]

Originally Posted by giantsforever
I read an anecdote about the power steering leaking a while after switching from Type F to Dexron, but I don't understand how that can happen?

Also, what's the difference between the two types of ATF?

Thanks!


1) In regards to causing leaks:
IMO, it's sorta like changing ATF in the tranny after waaaaaay toooooo many miles and causing issues. OR
the same can be said about an engine with waaaaaay toooooo many miles on conventional oil then switching to synthetic and causing leaks. Is is myth or fact? IDK!

2 )Differences:
I think the differences between the two ATFs are the friction additives/modifiers in Dexron(II, E, III etc.) as compared to Type F which I don't think has any.

 

[mechjames]

Using regular dex/merc atf which has friction modifiers will make your pump noisy and may cause the pump to wear out prematurely. I deal with a lot of 80's and 90's fords and type F is the stuff to use as they didn't switch them over to regular dex/merc until the late 90's / 2000's

If you really want synthetic Type F, then it's called Amsoil Supershift transmission fluid. Otherwise I usually just use pennzoil or castrol ATF.

 

[giantsforever]

Thanks, everyone.

mechjames, would you help me understand how the friction modifiers in Dexron make the pump noisy and wear it out prematurely?

Also, does it harm the power steering rack?

Thanks!

 

[BrocLuno]

The friction modifiers are for the clutch plates in an auto tranny. They have no effect on metallic parts.

Noisy pump is either worn, or wrong viscosity.

Leaks are worn bearings allowing shaft oscillation beyond what the worn seal can control, or worn hard cracked seals ...

 

[PeterPolyol]

As mentoined Dex has friction modifiers for clutch plates which are useless in your system and it's typically too VMed and/or too light (Dex VI) for what your Type F steering system is expecting. Since Type F is obsolete and hard to find, some auto mfgs have been recommending the most widely available and common fluid for decades now- DIII/M. It really boils down to how hassled are you to procure the fluid.

 

[giantsforever]

Thanks.

What does "VMed" mean?

 

[PeterPolyol]

'Viscosity modified'. It's most likely that there aren't any specific differences in viscosity modification between Type F and conventional Dexron III's but someone with experience in the industry could tell you with certainty

 

[giantsforever]

Thanks

 

[MolaKule]

Originally Posted by giantsforever
I have a 1988 Volvo 240 DL normally aspirated with power steering (ZF type). The manual calls for Type F. I'm wondering if I can use synthetic Dexron instead, because I can't find synthetic Type F and have lots of synthetic Dexron?

I read an anecdote about the power steering leaking a while after switching from Type F to Dexron, but I don't understand how that can happen?

Also, what's the difference between the two types of ATF?

Thanks!


Unless your PS has clutches I don't see why you would need Dexron III/Merc.

Amsoil's SuperShift is a type "F" and a synthetic:

Type F PSF

Most Type F is not used in racing applications so a synthetic base oil is not needed.

I do blend a synthetic type F for certain racing customers.


Originally Posted by MolaKule
ATF if a special hydraulic oil for the following purposes:
Lubrication for gears.
Cooling and heat transfer.
Transmitting torque via the Torque Converter.
Friction modification for clutch packs, bands, Torque Converter Clutch.

One of its more important duties of ATF is to make sure the fluid's coefficient of friction is matched to the friction materials inside the tranny. I.e., to ensure the proper static and dynamic coefficients of friction during engagement/disengagement.

In the early days of AT's the clutch material was composed of cellulose material with cotton and other soft materials in a phenolic resin binder. Today, hybrid materials are used.

Hybrid (or composite) materials are typically manufactured using a process similar to that used for paper-based materials, but using carbon fibers in combination with organic or synthetic fibers such as Kevlar and aramid fibers.

Many of the clutch materials from various manufacturers are close in terms of static and dynamic friction coefficients.

The clutch disc material of Automatic Transmissions, and other wet clutch applications, are made of porous friction materials which are bonded to steel core plates.

Friction materials may include cellulose, carbon fiber, Aramids, fiberglass, or a combination of materials (composites).

Today, composites are the norm.

Note: Sintered metal composites may be found in HDD applications.

This material must exhibit:

1.) Mu(o), low speed dynamic coefficient; affected by friction material ingredients and ATF additives adsorption

2.) Mu(i), initial dynamic coefficient at high speed; affected by hydrodynamic effects/porosity/compression/roughness.

When an additive company tests its ATF additive package, many transmissions are run through the SAE2 and other friction test machines (JASO M349-98, R-H Friction Apparatus, ZF GK Test Bench, Low Velocity Friction Apparatus, etc) to determine if the Friction Modifier set is appropriate.

The friction characteristics (Mu verses Velocity) of the clutch/fluid system are carefully monitored for each separate transmission and fluid formulation.

Mu is coefficient of friction plotted on the vertical axis, V is the relative speed of rotating components plotted on the horizontal axis. Mu(v) then is the resulting curve of the frictional characteristics of the clutch/fluid system.

The appropriate FM additive type and levels are then determined for the complete additive package...

The exact composition of and specific chemistry (molecular structure) of the Friction Modifier(s) are closely guarded secrets.

With the many different chemistries and potential mixes available, I think one can now see why Mutli-Vehicle fluids can be manufactured.

Ford Type "F" ATF is a fluid with very low levels of friction modification and has a Mu(V) curve separate and apart from either the Dexron Series or the Chrysler ATF+ series.

Ford Type "F" ATF is often used today in racing transmissions such as the PowerGlide and TH400 Turbohydramatics because of the positive lockup, IE, little to no slip in the clutch packs during engagement.

Chrysler ATF+ fluids are on the other end of the spectrum and exhibit a completely different Mu(V) characteristic. The ATF+ fluids are highly friction modified.

For a more Technical Study on ATs and heat transfer one can go to:

https://www.bobistheoilguy.com/automatic-transmissions-study/

 

[dave1251]

I would just keep using type F. The car is 31 years old.

 

[dave1251]

On Volvo forums users have stated DEX III caused thier seals to fail. Yet Mobil One ATF works well. Just more information which is clear as mud.

 

[qdeezie]

For what it's worth, my '90 F-150 whines if I use a cheap Type F ATF such as Supertech. However, it doesn't whine when I use Valvoline Type F.

Not sure if it adds any value to the thread, but just putting it out there that I have experienced a whine between two different Type F fluids. I've never tried Dex/Merc in my PS system to know whether or not it whines.

 

[giantsforever]

Thanks. I found some Chevron Type F in my garage and also Pennzoil, both dino. Where does the Pennzoil Type F fit in the quality category? Thanks

 

[qdeezie]

Originally Posted by giantsforever
Thanks. I found some Chevron Type F in my garage and also Pennzoil, both dino. Where does the Pennzoil Type F fit in the quality category? Thanks


You'll likely be safe with both Chevron or Pennzoil. Both are extremely high quality.

 

[Linctex]

If it were my car, I'd probably be running used (but well filtered) 0W-20 in that pump.

 

[MolaKule]

Originally Posted by Linctex
If it were my car, I'd probably be running used (but well filtered) 0W-20 in that pump.



Doesn't sound like running a contaminated MO in a PS system is a good idea to me.

If you think you'll need a thicker PSF type F, then,

https://www.redlineoil.com/Content/files/tech/RACING_ATF_PROD_INFO.pdf

 

[Kamele0N]

So you are basically saying that 0w20 oily water is not even good enough to be used in simply PS pump...

 

[ka9mnx]

Type F and Dexron are totally different animals. Use Type F only if that is what your vehicle calls for. Ask me how I know!