MAINTENANCE
Transmission fluid needs to be changed from time to time in order to extend the life of the transmission. This is usually every 30,000–60,000 miles (48,000–97,000 km), and sometimes more – check your owner's manual for service intervals. When the transmission fluid gets old, you might have trouble shifting or your car may get sluggish or stall when at rest. You can consult your owner's manual to find out how often you need to change your fluids, but you can also learn to diagnose and address the issue yourself.
Here are some tips:
Check the level of transmission fluid first by using the dipstick. Automatic transmission fluid (ATF) is the fluid used in vehicles with self-shifting or automatic transmissions. It's typically colored red or green to distinguish it from motor oil and other fluids in the vehicle. On most vehicles, you can check the level with a dipstick while the engine is running.​
Look for the transmission fluid dipstick, which is usually red-handled. It should be labeled clearly and easy to access, on most cars, close to the oil dipstick. Dipsticks list a hot and cold reading. If your engine has not been run in about an hour and you do not live in an extremely hot climate refer to the Cold Reading for proper levels.
If your levels are low, but the fluid looks clean, you might just top off the system. If the fluid looks discolored or sludgy, you need to change it. If you're at the mileage marker that requires you to change your transmission fluid, you might just elect to change it anyway, even if the fluid looks good.