ATF vs PSF in GM system

[HyundaiAbuser]

2011 Silverado had a power steering pump start whining so I decided to flush the fluid with the plain prestone psf. After which it began whining substantially louder which lead to the decision to replace it. After replacing the pump, it was flushed with acdelco 105074 and re-bled to which the new pump began whining relative to rpm. Out of frustration I flushed it another time with Maxlife ATF which quieted the pump. Now there is no trace of the previous whining. What could be the reason for this and has anyone else experienced something similar?

 

[mattwithcats]

GM power steering usually uses either…

Dexron III, cheapest
Dexron VI, slightly thinner than Dex III, almost the same price
and TES-295, same viscosity as Dex III, but full synthetic like Dex VI….

 

[Snagglefoot]

As far as hydraulic power steering goes , GM specifies their power steering fluid. Equally important is that you bled the air out of the system. Perhaps you bled it better one time than the other. Also, old return lines might be allowing air to get back into the system. I use their power steering fluid and have done so for 14 years. Make sure the power steering pulley is flush with the end of the shaft.
Here is a 2011 owners manual.

 

[BrianF]

Not sure of the specs but I didn't seem to care either. My 2006 Trailblazer had nasty whine in the winter. In 2012 I did a bunch of drain and fills with some Amsoil ATF and later on some Group 4 ATF. It really helped down to -30c but around there and beyond it still whines a bit. Other than that, the pump runs great!

 

[dan_erickson]

On my 2013 Tahoe I came to the same conclusion that maxlife atf seemed to run the most quiet.

 

[JavierH19]

Odd that i have 315k and 197k on my pumps and neither have failed. Only the 315k has a little bit of whine but i haven't changed the fluid in like 50k. Maxlife is around 5.9 cst while almost all the rest on the shelf are 7-7.5. don't know what else it could be.

 

[repairman54]

Did the suck out partial and refill with GM power steering fluid in my '11 Tahoe at 50k. Quiet at 135k but due again for the same treatment.

 

[wlk]

My 93 C1500 had a bad whine in it last Jan, I had been doing siphon and replacing w plain ps fluid every other month for over a year since I bought it. I made the mistake of adding Lucas ps thinking it would help but it was so thick everytime I started it I thought the pump was coming apart by the horrid noise it made. Flushed it out w Maxlife after a few days and whine is gone thankfully.