Transmission fluid is red in color. It will get darker as it is used to shift gears and lubricate the clutches inside the transmission. The clutches wear and leave behind small particles that can cause the valves to stick. Causing the transmission to shift harshly.

Transmission fluid replacement is recommended every 30,000 to 60,000 miles. The best practice of changing the fluid is to have it flushed out with a transmission flush machine. Using a machine ensures all the fluid is replaced, not just what is in the pan. Some vehicles come with a changeable filter inside. Those should also be replaced when doing a transmission flush.

Some newer vehicles, like those equipped with a CVT, may have longer recommended service intervals. The transmission fluid acts as a coolant and a hydraulic fluid for the transmission. The control valves inside the transmission need clean fluid to make shifting smooth.

Transmission fluid is a petroleum base fluid and needs to be replaced just like your engine oil. Transmission fluid breaks down from the heat in the transmission and over time.

Regular maintenance helps prevent transmission problems and extend the life of the transmission. If you notice signs of slippage or the fluid has a burnt odor, or discoloration, it is time to have the fluid checked.