Type F was originally used in the Ford trans that used "asbestos" linings and would slip with conventional fluids. It has "gripping ability" in it for the clutches it was designed for. Reason it shifts "harder" in a trans that uses paper clutches. Paper clutches don't need the additives that F has since they were designed a little differently and fluid requirements changed. I have found that like Nick says, the higher the horsepower, the less you need the type F. Lower horsepower cars get away with F and some go 50/50 mix of F and Dexron. I was good at 350-400hp cars using F and then above that troubles started showing. People asking me to freshen up transmissions when the fluid started turning dark and yet the trans still worked perfect. No destructions at those times. Soak new cluches in Dexron, reseal trans components, check endplays and down the road without troubles.