Does ATF naturally get low over time?

[Jack Smith]

I have a 2010 CRV with ~30K and a 2010 Corolla with ~40K. Make very short trips everyday to work for about 2 miles one way. Therefore the mileage for both cars is so low. Have never checked the automatic transmission fluid (ATF) in either car until today. And realized that both cars have very low ATF, much lower than the lower dot. Will do a ATF drain and fill tomorrow. But just wondering whether it is natural for ATF to get low over time? or does this indicate that the transmissions are worn? Thanks a lot for any comments/answers.

Topic

[Joe Mama]

Since transmission hydraulics operate in a closed system, once filled, the ATF level should never drop.

Therefore, the only indication of low ATF is an external leak.

[Jack Smith]

Thanks a lot! But, this is really strange. Both of my cars park in the garage. And, I keep a close eye on leaks. There is really no oil marks of any kind on my garage floor. I also check the transmission (when I was changing oil over the weekend — which was why I decided to check ATF in the first place). I didn’t see any signs of leaking either. Both of them are quite clean.

[Joe Mama]

Other possibilities:

ATF fluid was intentionally left low during routine maintenance (transmission flush perhaps) because it’s easier to leave it low & add later…. than to try to remove fluid from an overfilled transmission (which can be difficult & messy.)

ATF fluid level was not checked properly; therefore, possibly indicating higher than it actually was at the time of service (or in this case, indicating ‘low’ when it could be actually ok.)

Any leaks are so small they are hard to detect and/or only leak under temperature/pressure demand (outside of your garage)

You can rule a lot of these things out by filling your system and seeing if the fluid level ever goes back down.

Be advised: unlike any other automotive fluid, the transmission fluid level must be checked via a certain established procedure (listed in your owners manual.) Here is an example of how to properly check trans. fluid:

[Jack Smith]

Thank you so much! I will do a drain and fill over the weekend. Then, keep a close eye on the ATF level in both cars.

[ratdude747]

Did you check the fluid with the engine running or off? Honda automatic transmissions are odd in that you check the fluid with the engine OFF. I can’t remember if should be warm or cold though… Eric has a video on this. Either way, if you check it with the engine running, based on a comment he made when doing a video on the 1999 Civic DX (the two rebuild special), the fluid will read LOW.

Otherwise, pretty much every honda uses 3 quarts of honda ATF. Not Dextron/Mercon or ATF+4. If it says “for honda”, and it’s ATF, then you’re fine.

[Jack Smith]

Thanks a lot for the reply. Yes, I was always confused about this, which was why I never check ATF before. Honda is different from Toyota.

For my CRV, I let the engine warm up until the fan kicked on. I then went through all the gears. Then, shut off the engine and checked the ATF level.

For my Corolla, I drove 5 miles on highway until the engine come to the normal temperature. I then came back to my garage and went through all the gears. Put it in “P” and left engine running, and checked the ATF level.

I believe I performed this correctly.

[EricTheCarGuy]

Very glad to hear you’re checking the fluid level correctly. Can’t tell you how many Honda transmissions I’ve seen ruined because someone did not check the level correctly.

As for changing the fluid, this procedure works for just about all Hondas. BTW I believe yours takes about 2.7 quarts.

More stuff about transmissions.

http://www.ericthecarguy.com/faq/solving-transmission-problems

Please keep us updated on your progress.

[Bluesnut]

If the fluid is low that means an external leak from something like a converter seal, axle seal, etc OR fluid is being lost into the engine cooling system through a leaking radiator fluid cooler. The latter usually shows up as kind of a sludge in the radiator.

You should also get in the habit of checking not only the trans fluid but all fluids on a regular basis. You should never assume that any or all of them are fine.

Running an automatic low on fluid can also be damaging to the transmission. If the transmissions act up at some point in the future then you will know what caused the problem; low fluid.

[Jack Smith]

Thanks a lot, Eric and Bluesnut! I have to say I am very surprised that both cars have significantly low ATF levels. Both cars were bought new ~6 years ago, were never driven hard and have very low mileage. I have never done anything to either transmissions (I doubt the dealers did anything when I brought them in on a couple of occasions for warranty and recall services), I never even pulled out the ATF dipsticks on either car until a couple of days ago. Especially, for the corolla, they say the ATF is life time. There is no instruction of how to check ATF levels in the owner’s manual.

[Bluesnut]

That lifetime transmission fluid is a bogus recommendation I don’t care who makes it and lifetime trans fluid is not the only hokey recommendation espoused by car makers. Oil changes every 10-15k miles, never a need to check valve lash, etc are other recommendations that can be harmful to your car.

These recommendations come out of the PR flacks in the marketing department and the goal there is to promote the idea that the car needs very little maintenance. From a mechanical point of view those recommendations are bad; from a sales point of view they’re great because the potential car buyer feels they will have to do very little to keep their vehicle in top shape.

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