I know this is kind of an older thread but I figured id put my 2 cents in. Im with Lonnie although I don't know who he is ,but I don't like any of my customers to run synthetic fluid in my hi perf. trannys even though that's what most of the newer trans. and manufacturers are running. The reason for this is the synthetic fluid is thinner and they are making the lube circuit holes smaller for gas mileage purposes. Also it is slicker, which is not good for hi perf. transmissions. I prefer a higher coefficient of friction, or more grab in laymans terms, for a performance transmission.The type F or ford fluid or b&m's fluid is good even the old school dex. mercon 3 is better than the synthetic fluid for our purposes, in my professional opinion. I recommend any of these fluids for use in my trannys. now in saying that the newer synthetic fluid will also run a little bit cooler than the older fluids, but what I also use is an additive called lube guard, they make several different kinds, but I use the platinum in a silver bottle, can be gotten at oreillys. this has a friction modifier in it and will also lubricate the valves and will drop operating temps. up to 20 degrees. if you don't believe this look at what the manufacturers tell you to put in a modern differential with a posi or one with clutches, its not synthetic ,too slick, even they learned there lesson on this, as it will void your warranty, not enough friction to grab the clutches.