Dextron VS FA

Seems Adam as usual, is closest to correct The only difference between the current + Mopar trans fluids is the base stock. +3 uses a conventional GpII base, and +4 is a semi-syn GpIII base. They have the same add packs, blended to meet the Chrysler 7176E spec. They are basically interchangeable, +4 just lasts longer and runs cooler. Despite being alot cheaper in recent years, +3 is not available anywhere I've been in the past year or so, so it's really a moot point.

You can run +3, +4, DexIII, the new DexIV, or even TypeF in the older 727-based autos. They will all work fine, not hurt anything, just behave a little differently. You'll get smoother shifts but more heat with the + fluids. Dexron II/III was the original factory fill. DexIV would be the technically correct best substitute, but cost the most. It'll shift crisply and being a GpIII based oil, last long and run cool. Run TypeF if you want the firmest possible shift and change it more frequently.