Originally Posted By: 440Magnum
Originally Posted By: sunfire
Originally Posted By: G-MAN
There actually isn't that much difference between the CF of ATF+4 and Dexron III/VI or Mercon V.
So what are the differences between the ATF specs? I thought CF and the friction modifiers were the main differences. That's why the ATFs are not interchangeable.
For one thing, small differences are important.
For another, its not JUST the "coefficient of friction" that matters, and CF itself isn't just one number. In the case of ATF+4, what matters most is that the sliding (dynamic) and still (static) coefficients of friction be as close to one another as possible. If the static CF is much greater than the dynamic CF, then what happens as a clutch engages is that just before its fully engaged, the static CF takes over and the clutch "grabs." The sudden loading of the grabbing action then starts the clutch slipping again at the lower dynamic CF, and then the "grab" occurs again. This is what causes torque converter clutch "shudder" and why ATF+3 (and +4) were designed the way they are. If the static CF is very very close to the dynamic CF, then there's no sudden "grab" as the clutch engages.
Great explanation. Thanks
By any chance are you some sort of engineer EE or ME?