The fluid level in the automatic transmission should be inspected by means of the dipstick after the transmission has been warmed up to ordinary operating temperature, approximately 158'F to 176'F. As a rule of thumb, if the graduated end is too hot to hold, the fluid is at operating temperature. The fluid level is proper if it is in the hot range between hot maximum and hot minimum.
NOTE: The cool level found on the dip stick should be used as a reference only when the transmission is cold. The correct fluid level can only be found when the fluid is hot.
It is important to keep the fluid at the correct level at all times to ensure proper operation of the automatic transmission. If the fluid level is too low, the oil pump will draw in air, causing air to mix with the fluid. Aerated fluid lowers the hydraulic pressure in the hydraulic control system, causing slippage and resulting in damage to clutches and bands. If the fluid level is excessive, planetary gears and other rotating components agitate the fluid, aerating it and causing similar symptoms as too little fluid. In addition, aerated fluid will rise in the case and may leak from the breather plug at the top of the transmission or through the dipstick tube.
In addition, be sure to check the differential fluid level in a transaxle. This fluid is sealed off and separate from the transmission cavity in some applications.
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