V8 guys - Power steering fluid or Transmission fluid for steering?

[lehiguy]

I see ATF as the superior fluid. How much stress is an auto trans under when your Cummins is pulling 15,000 pounds down the freeway at 80 MPH? Certainly more than a steering system would ever be. Dodge has a PS noise isssue a few years back, the problem was solved (this was a TSB) by switching to synthetic ATF in the steering system. That's all I ever run.

 

[GLTHFJ60]

I run ATF in my system, saginaw pump and Toyota box. The original lines aren't holding up to the pressure well, but other than that, it's all good. No noise and great power.

 

[boots4]

The additional additives in ATF can harden seals if the manufacture didn't recommend that fluid for your system. For the year range of Saginaw pump I run PSF is recommended. I'm switching to PSF because when I rebuilt my pump the seals were pretty hard and it's recommended.

I did like the convenience of only having to carry one fluid for the tranny and PS but in reality a bottle of PSF doesn't take up much room. I bet the steering pump can see lots of stress when big tires are being turned against rocks on a challenging trail and I'd say an environment that exceeds 1000psi (for me in the 1600psi range due to mods) has probably got some stress in it.

 

[lehiguy]

The additional additives in ATF can harden seals if the manufacture didn't recommend that fluid for your system. For the year range of Saginaw pump I run PSF is recommended. I'm switching to PSF because when I rebuilt my pump the seals were pretty hard and it's recommended.

I did like the convenience of only having to carry one fluid for the tranny and PS but in reality a bottle of PSF doesn't take up much room. I bet the steering pump can see lots of stress when big tires are being turned against rocks on a challenging trail and I'd say an environment that exceeds 1000psi (for me in the 1600psi range due to mods) has probably got some stress in it.

If ATF hardened seals, automatics would die pretty quickly since they rely on hydraulic pressure (meaning there are seals) to do anything. Internal leaks are the most common cause of automatic trans failure. There are many different types of ATF, I can't say what the differences are, but I'm willing to bet that they all swell seals in order to keep the trans going.

 

[boots4]

I'm saying ATF can harden seals in power steering pumps where PSF is recommended and that's actually what I saw when I rebuilt mine due probably to the age and the ATF I have been running in my system. Tranny seals are designed to run ATF and in that application I agree that ATF will swell the seal. Some power steering boxes are also designed to run ATF but the GM saginaw pump of my vintage recommends power steering fluid. I'm certainly not saying you have to run PSF but that these are the reasons I'm running PSF.

 

[ntsqd]

Are there any other seals in a Saginaw PS pump other than the shaft seal up front?

 

[boots4]

Are there any other seals in a Saginaw PS pump other than the shaft seal up front?

Yes, there are these two internal to the pump. Some housing seals on the front of the "ham" and then some for the bolts that hold the "ham" to the pump.

 

[bloc]

Digging up a really old thread..

I was curious whether anyone new had any definitive info? or the guys putting ATF in the system developed leaks at the pump?

I'm leaning toward ATF because I'd much rather rebuild the pump on the engine than the box on my 80-series.

To those saying ATF isn't rated for the pressures seen in a PS system.. it is what Toyota recommended for the PS system in landcruisers already.. Surely the GM pump won't produce that much more pressure?

 

[MANUCHAO]

@bloc i have been running PSF since 2011... the steering box is starting to leak, but i don't think the PSF is the reason for that.. i got the box with some 200k on it and i here never serviced it... it has well over 300k now... I'm planning on swapping this one while i rebuild the other one with the 100 sector shaft...

Personally i don't think it makes much diff what fluid you run.. but yeah it would be cheaper to rebuild/ replace the PSP...

 

[franklin40]

reviving an old thread again. i have a chevy power steering pump and a mini truck box. should i use power steering fluid rated for north american cars or the toyota ps fluid?

i have this but maybe i should get the toyota stuff to protect the box?

my swap is in my 40 but this thread is in the 60 series section. still applicable though for those with chevy/toyota mixed systems. i’m thinking i’ll run toyota power steering fluid as chevy pumps are cheap to replace

 

[NCFJ]

I use PSF in my swaps. Just do.
Past that, the best thing you can do is keep the fluid cool. I run a Derale cooler same size as the trans cooler.