Q: How do you accurately check your automatic transmission fluid? Hot, cold, running, put all gears through, then check?

asked by on

transmission fluid check, see above Thanks

Typically, the fluid level is checked both hot and cold in order to provide a cross check. Checking initially when cold is easier as you are not hovering over a hot engine holding a hot dipstick. Basically, on a flat level surface, start the vehicle’s engine and immediately run through each gear, pausing just momentarily.

Finish with the car in "Park" and leave it in "Park". Withdraw dipstick and wipe it clean with a LINT FREE cloth (lint and dirt causes problems in transmissions). Reinsert the dipstick after you have wiped it and upon withdrawing it. See if the fluid level is within the cross hatched area marked below a "C" (for cold).

Sometimes you have to look at BOTH sides of the dipstick in order to gauge the level. If the level is in the "C" area, you are likely OK, but to be sure, drive the car for about 10 miles and re-check the level, this time looking at the cross hatched area marked below the "H" (run through gears as before, and leave in "Park").

If the fluid level is OK when cold, it should also be within the cross hatched area for "H" as well. The reason for checking when both hot and cold is transmission fluid expands as it is heated. Note that if you drive the car at highway speed for a long period of time and then attempt to check the fluid level "hot" after that you WILL get a false reading (the fluid level will appear "high", when in fact, it is perfectly OK). So, when checking if it’s hot, you can’t do that check if you just drove 50 miles across the desert because the fluid will have expanded. Transmission fluid expands and keeps expanding the hotter it gets. Dipsticks are calibrated to "normal" hot operating temperature (i.e., the 10 mile suggested drive; longer in winter). If the transmission fluid has been in your vehicle for more than 100,000 miles, change both the fluid and the filter, which maintenance will help promote the longevity of your transmission. Modern synthetic transmission fluid of the right type is recommended. If you are in need of a transmission fluid service, a certified technician from YourMechanic can come to your car’s location to perform this.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. How do you accurately check your automatic transmission fluid? Hot, cold, running, put all gears through, then check?

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Car cranks slowly when it is hot, but cranks normal when the engine is cold

It sounds like your starter motor could be overheating. If the starter overheats, this can cause it to malfunction. I would recommend having your starter inspected and replaced as necessary by a certified mechanic. Once you have a new starter,...

Q: Does this transmission have a transmission filter that can or needs to be change at certain miles?

Most vehicles have an internal transmission filter that can be changed by removing the transmission pan. Some diesel trucks will have an external filter that can be changed just like an oil filter. The transmission filter is usually recommended to...

Q: My hot temperature light is blinking and the temperature is below the C mark. Is it safe to drive home?

Hi there. The coolant temperature sending unit is malfunctioning and sending the vehicle the wrong information or the gauge on the dash has failed. The sending unit could have burned inside causing the computer to think that the engine is...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...