Question about power steering fluid.

[Ruger]

Do you do the same thing for coolant in the radiator?

No.

 

[Chris@FreedomMotorsports]

I don't use transmission fluid in mine. I use power steering fluid. Although they have the same/similar viscosity, the power steering fluid lacks the friction modifiers and so forth that transmission fluid has in it and I have come to believe that those extra additives in the tranny fluid forming into trash in the system may greatly contribute to the common failures of the pump and rack. Using the actual power steering fluid I believe will help cut down on the risk of failure.

 

[Ruger]

Chris, can you please explain the function of the friction modifiers in transmission fluid?

 

[dkfc13]

I don't use transmission fluid in mine. I use power steering fluid. Although they have the same/similar viscosity, the power steering fluid lacks the friction modifiers and so forth that transmission fluid has in it and I have come to believe that those extra additives in the tranny fluid forming into trash in the system may greatly contribute to the common failures of the pump and rack. Using the actual power steering fluid I believe will help cut down on the risk of failure.

Chris,
Can you elaborate on the power steering fluid you are using? And the trash you are seeing in your system? Have you had your used fluid analyzed?

While PSF and ATF might be somewhat similar in viscosity at 100deg C, generally speaking PSF is about double the viscosity of ATF at 40deg C. The increase in viscosity can cause cavitation in your PS pump caused by inadaquate flow of the PS fluid at the pump inlet. Are you using the stock resivoir and inlet hose?

Running a thin fluid can also cause issues. Thinner fluid can cause internal leakage in the pump which will generate heat due to ineffiency.

Someone can correct me if I am wrong however; I believe ATF must meet a number of specifications that PSF doesnt. This includes rust prohibitor and anti-foam tests.

I am not aware of friction modifiers being an issue in non-clutch based systems however; I do know a lack of friction modifiers in clutch based systems (ie. auto transmission and some LS differentials) can cause noise and pre-mature wear issues.

As always when changing fluids, make sure you check compatability with your seals.

 

[Chris@FreedomMotorsports]

The friction modifiers in transmission fluid adhere to and assist the clutches in the transmission to hold tight to each other without slipping. The power steering system is a non-clutch type of system. That being said, don't get me wrong, I have not had anything tested, it's just a theory I am testing on my old Raptor. The pump went out due to cavitation and overall heat at the smokey run last year. When it happened, it amazed me how hot the fluid got while doing what amounted to some pretty easy offroading overall. When I took the system apart to install the new pump, I noticed that the stock reservoir was full of trash. I cannot say exactly what the trash was made up of, but it was reminiscent of the trash in the clutch fluid reservoir on my diesel pickups with manual transmissions. Those systems recommended synchromesh manual fluid and no brand I tried ever improved. However, since installing a new power steering pump I have used Amsoil power steering fluid, not because of anything scientific really, just because I like their brand fluids. The truck has seen some pretty hard miles offroad since, even seeing it's hardest ever offroad driving by my son at Havoc in the hills II where power steering systems were failing right and left, but even though my son was driving there harder than most, (he was actually trying to drive it like it was a full on trophy truck and he was Andy Burns behind the wheel while he showed off for his girlfriend). The result? Although the fluid still got hot, I didn't lose the pump and I didn't lose the rack. The conditions were sincerely extreme while Cullen was driving it there and the power steering fluid with all other stock parts weathered those conditions like a champ. I now have an ICON PS Solutions reservoir on it, but other than that and the Amsoil PS fluid, it is stock.

ALL of that being said, this is just a theoretical test I have been running on my 2011, I have not tested the fluids at any point, in hindsight I probably should, but this testing wasn't actually well planned, it was more of a thought I had one day that I ran with.

 

[pat247]

Chris, thanks for your input, I think you could be on to something with the friction modifiers. When I was reading through the capacities and specifications chart on page 301 of the 2014 OM it calls for MERCON LV in the automatic 4wd transfer case (has clutches), and calls for Motorcraft Transfer Case fluid in regular TC that is in the Raptor.

I'm curious as to why ford opted to not use pure power steering fluid. Was it a bean counter decision as opposed to an engineering decision?????

 

[Ruger]

I'm curious as to why ford opted to not use pure power steering fluid. Was it a bean counter decision as opposed to an engineering decision?????

I don't know, but it's not unique to the Raptor. My wife's Edge uses tranny fluid in the PS system, too.

 

[pat247]

I don't know, but it's not unique to the Raptor. My wife's Edge uses tranny fluid in the PS system, too.

Yeah but it is also a ford and the same bean counters.

 

[Trick.Raptor]

I don't know, but it's not unique to the Raptor. My wife's Edge uses tranny fluid in the PS system, too.

My old Nissan Titan used ATF for the PS fluid as well.

 

[dkfc13]

ATF has lower viscosity so it requires less power to pump through the system improving fuel economy.

This is an industry trend and is not unique to Ford. In fact TRW Uses ATF in their commercial truck power steering system.