Fluid - A/T: Description and Operation

The automatic transmission fluid is selected based upon several qualities.

The fluid must provide a high level of protection for the internal components by providing a lubricating film between adjacent metal components.

The fluid must also be thermally stable so that it can maintain a consistent viscosity through a large temperature range.

If the viscosity stays constant through the temperature range of operation, transmission operation and shift feel will remain consistent.

Transmission fluid must also be a good conductor of heat.

The fluid must absorb heat from the internal transmission components and transfer that heat to the transmission case.