CORRECT OPERATION

ATF viscosity must not change that much with a change in fluid temperature. This is because the transmission should operate (shift) similarly in hot or cold conditions. If the thickness or thinness of the fluid varied, internal flow would be different and lead to abnormal operation. Vehicle manufacturers generally require that ATF not solidify at -40° F. and not thicken at 300° F. If the fluid thickens at high temperature, the fluid will leak and cause the bands and clutches to slip.

The rotating parts inside the transmission naturally churn the fluid, so ATF must resist foaming. Air bubbles in the fluid would reduce its ability to transmit pressure, since air can be compressed, and the transmission would not operate properly. It would also impede lubrication, since there would be little actual fluid between parts. Help avoid foaming by not overfilling the transmission.

ATF must also not oxidize. Oxidized transmission fluid will form sludge on the components and upset the normal flow of the fluid. Some parts may even rust; the rust could foul the fluid, further impacting transmission performance.

SYSTEMS
AUTOMATIC TRANSMISSION FLUID
AUTO. TRANSMISSION FLUID CHANGE PROCEDURE
VARIATIONS