(Updated on September 30, 2021)
The same way an engine relies on motor oil, an automatic transmission needs to be lubricated with transmission fluid. It has several moving components which rub together just like the engine does.
Automatic transmission components can only work smoothly if they’re consistently lubricated while the vehicle is running. Any type of fluid leak would cause major problems for the transmission’s components and for the vehicle itself.
To ensure you have the proper amount of transmission fluid available, you need to regularly check your automatic transmission fluid to see what level it is at. Most auto manufacturers will recommend that you check the fluid level every 40,000 miles.
Of course, you can look in the owner’s manual for your vehicle to confirm the number of miles. If the manual suggests different mileage, then go with that number.
There may be times when you’ll want to check the fluid level earlier. For instance, if you shift gears in an automatic vehicle and it starts to hesitate, then you should check the fluid immediately. In fact, do this before you even go to the mechanic because they may try to sell you an unnecessary service.
Checking Transmission Fluid (Hot or Cold)
Below are the 5 steps for checking your automatic transmission fluid when the engine is hot or cold.
1) Prepare the Vehicle
The first thing you need to do is find a flat and firm surface for your vehicle to park on. Set the parking brake and start the engine. Let it run for about 5 minutes so that it can warm up.
Some car manufacturers will recommend you turn the engine off before checking the transmission fluid, but most don’t recommend this.
2) Find the Dipstick
Open the hood in the front and find the transmission dipstick. The handle of the dipstick should have a red or orange ring on it.
In a front-wheel drive vehicle, the dipstick for the transmission usually sticks out from the transaxle. If you have a rear-wheel drive vehicle, check toward the back of the engine and you should find the dipstick.
3) Check the Fluid Level (When Engine Cold)
Pull out the dipstick once you’ve found it and the engine has warmed up. Wipe it clean with a rag and reinsert it all the way in. Now, pull out the dipstick again and observe the markings.
There are typically two marks spread out on the dipstick and are usually labeled “Cold” and “Hot”. Sometimes they may be labeled “Add” and “Full”.
Other times there may be no words. Dots, notches, or lines next to each label provide a fluid level range you want to be in. Since the engine is barely warm at this point, you want the level to be somewhere in the “Cold” or bottom range.
4) Check the Fluid Level (When Engine Hot)
To get an accurate transmission fluid level reading when the engine is hot, you will need to check the level after normal driving (idling in the driveway is not enough). Usually, driving about 10 miles will do the trick (slightly less if on the highway; slightly more if in winter).
Once the engine is hot, repeat the same process as step 3 above. Be careful since the fluid and engine will be very hot so you can easily burn yourself. When you look at the measurement, you’ll want the level to in the “Hot” range.
5) Add Fluid if Necessary
If the fluid level was below the “Cold” or minimum mark on the dipstick when the engine is cold, then you need to add more transmission fluid to the transmission.
If the fluid level was below the “Hot” or maximum mark on the dipstick when the engine is hot, then you need to add more transmission fluid to the transmission.
Make sure you choose the right transmission fluid, though, because not all fluids will be compatible with your vehicle’s transmission. The best way to figure out which fluid to use is to check your owner’s manual.
When you’re ready to add the fluid, put a funnel in the opening of the tube and slowly pour the fluid into the funnel. Add the fluid slowly and keep checking the fluid level until you get to the correct mark.