Check the fluid in five steps
- Warm it up. Drive 10 to 15 minutes so the fluid reaches normal temperature. Most dipsticks are marked for hot fluid.
- Park on level ground. Set the parking brake and leave the engine running. Put the shifter where the owner's manual says, usually Park; some vehicles specify Neutral.
- Find the transmission dipstick. It is usually toward the back of the engine bay and often has a red, yellow or labeled handle. Do not confuse it with the engine oil dipstick.
- Pull, wipe, reinsert, pull again. Wipe it with a clean, lint-free rag, push it all the way back in, wait a second and pull it out. Read the level against the HOT range.
- Look and smell. Put a drop on a white paper towel. Note the color (bright red, dark red, brown, pink and milky) and whether it smells burnt.
Checking the fluid takes five minutes and tells you a lot: whether there is a leak, whether the transmission has been running hot, and whether it is time for service. Many newer vehicles have no transmission dipstick at all; for those, the level is checked at a fill plug on a lift, and the job belongs in a shop.
What the reading means
Within the HOT range: the level is fine. Below it: the transmission is low, and since transmissions do not use fluid the way engines burn oil, low usually means a leak. Above it: overfilled, which can make the fluid foam and vent. Add fluid only of the type the owner's manual names; the wrong fluid can change how the transmission shifts. The fluid types guide explains why.
Color and smell
New automatic transmission fluid is usually bright red and nearly odorless. With age it darkens. Dark brown or black fluid that smells burnt points to overheating; pink and milky fluid can mean coolant has mixed in through the cooler, which needs attention right away. The fluid color guide has a chart.
No dipstick?
Many vehicles built in the last 15 years or so have a sealed transmission with no dipstick. The level is checked at a fill or check plug, often at a set temperature with the vehicle level on a lift. Without the right equipment it is easy to get wrong, so leave it to a shop.
When to call the shop
- The level is low, or you see a red or brown spot under the vehicle
- The fluid is dark and smells burnt
- The fluid looks pink and milky
- The level is fine but it still slips, shifts hard or delays into gear