Quote:
Originally Posted by Lubehead
Actually, I don't think there's anything low grade about modern automatic transmission fluids. In fact they are amongst the most complex fluids available. Automatic transmission fluids typically contain antioxidants, antifoam agents, viscosity modifiers, antiwear additives, friction modifiers, and seal swell modifiers.
Formulations vary from manufacturer to manufacturer with sometimes subtle differences in friction modifier chemistry. The oxidation resistance of these fluids is especially high, allowing the long service life now generally reccommended by most OEM's.
In addition to acting as a hydraulic fluid, these products also lubricate gears and bearings, and must be able to withstand severely low start up temperatures as well as extremely high bulk oil temperatures particularly in severe service like towing.
The high temperatures ultimately take a toll on the fluids life as byproducts of oxidation accumulate in the form of depleted antioxidant inhibitors and contaminants from the clutch plates, as well as oxidized base oil.
Changing the fluid in a timely fashion cannot help but provide extended component life. Keeping the fluid relatively clean and fresh enables it to effectively deal with preventing the inevitable results that would occur if it was not changed. Reduced wear, reduced deposit formation and superior performance in both cold and hot temperatures is ensured by a proactive approach to fluid maintenance.
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I don't think there is anything low-grade about these ATF fluids either. I just think that the lubrication requirements are not particularly demanding. That is why a straight 5w oil like an ATF works fine. It is a sealed system, with a pressurized oil bath. It is heated when cold, and cooled when hot. All of the other requirements are very specific, and critical, but they are not as related to the lubrication aspect. And when people talk about changing the fluid, they tend to focus on the lubrication requirement.
I do think that the friction modifiers are more critical than you give them credit for.
I also think that the thermostatically controlled heat exchangers in the X5 deal quite successfully with the high temperatures that used to make transmission fluid changes much more critical.
A lot of the transmission failures we have seen reported have been in the transmission valve bodies. Those aren't caused by lubrication failures. Many other transmission failures have been caused by electrical failures, either wiring harnesses, solenoids, or sensors. I suggest that changing the transmission fluid regularly will have little to no effect on transmission life considering these common failure modes. If we were seeing burnt clutch plates and other signs of overheating, I would fully agree with you that changing the fluid regularly would be of benefit.
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