904 Transmission Fluid Recommendation

The testimony of the oil rep is too broad. Did his side win? Any fluid "might" work with most transmissions and not necessarily cause immediate or obvious failure, but it can't be good for it over the long term. It mainly depends on the formulation of the fluid and application of the trans. You said yourself that Type F feels different from Dextron, likely because there is less slippage in the same application. The newer the trans with more electronics, the more important that the correct fluid be used.

I agree that many trans failures after a fluid change are not the fluid's fault even if it's not the same/correct fluid. I've seen many people think that a change will eliminate slight slippage. But that actually means it's too late and the trans is already malfunctioning. New fluid can also act as a "cleaner" and loosen up any varnish, sludge, clutch material, etc. build-up inside, which can interfere with the trans functions.

I also realize that manufacturers try to sway people to use specific brands (like their own) making it sound like other brands may cause issues. But there are laws outlining that properly formulated fluids by other brands can be used without jeopordizing the warranty.

But bottom line is that there has to be a wider variety of transmission formulations for specific applications if one is to expect the proper performance. i.e.: Nobody will convince me that putting a Type F fluid in my 2004 Dodge dually diesel is ok!

Also, while synthetics may not be necessary in most applications, the harder a trans and converter is worked (race, towing, etc.), the better the synthetic fluid will hold up and help extend their lives over conventional fluids. Good insurance!