What makes an ATF cause pump whine?

[bulwnkl]

I experience pump whine from my A/T when I use a particular ATF, but not when I use another. What about the ATFs would cause pump whine when using one but not the other? The whine is not severe, but I notice it. Both are recommended for this application.

I'm NOT asking for suggestions as to what fluid to use, or what is best. I'm simply curious as to what causes this observed fact, and whether there's any significance to it.

 

[440Magnum]

One probably resists cavitation better than the other for some reason. Viscosity difference? Thicker fluid more likely to cavitate.

On the other hand, a thicker fluid might be more likely to damp the mechanical noises the pump makes.

 

[69GTX]

Besides the viscosity I would think that synthetic vs. conventional, as well as a stout additive package vs. a weak one could make a difference as well. What might be audible to one person, might not be picked up by the next.

 

[demarpaint]

I'm thinking it's a slightly different viscosity.

 

[MolaKule]

Check for overfilling or underfilling.

Barring a coincidental worn pump with leakage, I have seen both of the above cause this.

How do you know for sure it's pump whine? A torque converter can cause whine as well when air entrainment is present.

You didn't state what the fluids were when you changed was from A to B, or the tranny make and model.

 

[bulwnkl]

Of course. Here you go:
It's a Honda 5-sp A/T in their pickup. The fluids in question are Honda's DW-1 and Red Line's D6. This has happened each time I've put D6 in, and it moderates or eliminated when I go back to DW-1.

As to fill level, all I can really say is that I check them both as directed in the owner's manual (and set them to the same level, of course).

The whine could be from the TC. It is the same kind of whine as any of the myriad vane-type hydraulic pumps I've owned and worked around in agriculture forever. Of course, this means it does not sound like the piston pumps in the tractors. ;-)

Air entrainment crossed my mind, as that has certainly led to whine in a system with low fluid in other applications. I have never seen bubbles on the dipstick when I check the fluid, but I don't have any other decent way of getting a look at the fluid.

 

[dlundblad]

My original thought was, "Is this whine caused by a multi-vehicle ATF that is 'suitable' for use in a Honda?"

From what I have seen here, it's best to stick with Honda ATF in a Honda.

 

[TurboFiat124]

I noticed the same thing with my Chevrolet van. I changed the transmission filter and topped it off with fresh fluid and I swear the van now sounds quieter.

I have no idea what was in it but I used O'reilly's store brand DexMerc rated for Dextron III and a WIX filter.

 

[DWC28]

Resurrection.
I have been working on an ATF top treat for pump whine and would like to share some observations and solicit comments.
Newer high performance, high pressure ATF pumps and smaller sumps both contribute to more pump whine. GM defines three different whines; launch whine, continuous whine and gravely sound.
Additional anti-foam additives may reduce this noise.
Anti-foam additives work in part by being insoluble in oil. Conventional wisdom holds that higher levels of anti-foam actually degrade air release performance.
Conventional ATF contains 3 - 10 ppm silicon.
Air causes pressure ripples due to implosion of air bubbles; this is manifest as pump whine.
This can be reduced with a fluid containing at least 30 ppm Si.
In hydraulic pumps the act of adiabatically compressing any entrained air causes the surface of the air bubble to reach high temperature, in some cases greater than 500C. At this temperature anti-foam is subject to thermal degradation.
Anti-foam being insoluble in oil winds up on drum surfaces, trailers and other places during transportation. An after treatment can solve the degradation and separation issues.
Finished ATFs are now being formulated with up to 50 – 70 ppm Si to prevent this problem.
Balancing the formula is extremely important and may require up to 20 different additives in finished ATF.