Packard Forum Index » V-8 (1955-56)

Previous owner used type FA in mine and it seems to work well overall.

https://www.napaonline.com/en/p/NOL75205

Quote:

I hadn't heard of Type AF, so had a little look online. Some say AF and F are the same, that type AF is just an updated version of type F. Some say AF is better than Type F for older transmissions, that it has different friction modifiers.

Does anyone know for sure if they are different and if one or the other is better for an Ultramatic?

*I have Pennzoil Type F in my Ultramatic and it seems to be okay.

FA is basically just F that is upgraded for longer service life. Its friction properties are the same as F.


I have an old car magazine from the 1960's sitting in my library somewhere that has an article talking all about the characteristics of the different types of transmission fluids and how the transmissions were designed to work on each of them. It's been a long time since I read it. I wish I could find it right now.

Basically, from what I can remember, Dexron produces a smooth slide into engagement, so the valve body is calibrated to apply the clutch quickly and let the fluid do all the work of smoothing things out. Meanwhile, Type F tends to slip a lot at first then suddenly grab, so the valve body is calibrated to apply the clutch much more gradually. I do not remember it saying anything about the old Type A fluids.

Those differences between Dexron and Type F were only during dynamic friction situations where the clutch is slipping during a shift. I think it said that the static or holding friction properties are the same between them, which means Type F will do nothing to stop your direct drive clutch from slipping under load.