Transmission fluid should be checked when the liquid is within the temperature range of 104°F to 113°F. Ideally, you’ll be checking it when the vehicle is running to get a more accurate reading.
The operating temperature for the automatic transmission in a running car is around 175°F. This is because transmission fluid, like all other fluids, expands when it warms up and contracts when it is cold.
How Do I Check Transmission Fluid Level?
Turn your engine on, engage the parking brake, and leave the vehicle running for a few minutes to allow the transmission liquid to expand sufficiently. You can check the reading now with the help of a transmission fluid dipstick. It is similar to the engine oil dipstick and needs to be dipped into the transmission fluid to get a reading.
The fluid should be clear, free of particles and odors, and look pinkish-red on the dipstick. Sometimes the liquid is brownish and a little thicker than fresh transmission fluid, this is alright but not ideal. You can also take and rub some between your thumb and forefinger to detect particulate matter and burnt smells. It will need to be drained and changed if the appearance, texture, and odor are not as expected.
The latest car models in the market are not equipped with a transmission fluid dipstick. Instead, you can check the internal computer to get a reading, or there’s a plug located on the side of the transmission that a trained mechanic can use to check the fluid level.
Checking the transmission liquid after the engine has been turned off for a while will give a false low fluid reading. But, in a few cases, the engine needs to be turned off before taking a reading, like when reading automatic transmission fluid levels.
How Frequently Should You Check Transmission Fluid?
As a rule of thumb, you should check on transmission fluid levels every six months. If you live in dry, dusty, and arid areas, you should get it checked more often. You should also perform transmission fluid flushes after clocking 30,000 miles.
If you find greasy puddles underneath your car, difficulty shifting between gears, non-engaging transmission, clunky sounds or burning smell when you turn on the vehicle, or your vehicle shudders, shakes, or lurches at frequent intervals, you’re long overdue a transmission fluid check. Low levels of transmission fluid lead to many of these problems and should be fixed as soon as possible.
How Do I Know if the Transmission Fluid Is Overheating?
Transmission fluid that has turned dark brown or black in color is an indication of transmission overheating. Another indicator of overheating is the fluid burning smell. Low fluid levels can also cause transmission overheating.
To sum up, use a transmission fluid dipstick to check transmission fluid level when it is hot, not when it is cold.