Synthetic A/T in 4r100???????

I am not convinced that it is that much of a plus for a tranny. Sure it can take more heat than regular ATF fluid but the tranny seals cannot so that fact that it can means little. A tranny properly serviced with dino ATF and properly cooled will last a very long time.

----------------- The SnoMan

ATF is specially formulaed so as not to foam causing a change in pressure..... I have never heard of synthetic ATF.Use what the manufacturer recommends and drop the pan rather than flush. Engineers spend a lot of time ensuring the ATF they recommend does its job in the transmission. If you have one of the early 4R100 98-99 they had a lot of warranty units around. Never did figure out what the problem was.