auto transmission fluid

[flameisley]

I have a transmission leak so I checked the fluid levels and it's just a bit below low. Is this transmission fluid okay to top it off? I did some research but could not find a straight answer. Also, how much should I put? Half a quart, the whole bottle? I'm a newb so I really have no idea.

[Wildthings]

It is fine. Do check the level of the gear oil in your final drive, if the level is high and/or it appears there is ATF mixed with the gear oil, you may have a leak between the two boxes which needs to be fixed ASAP.

[AtlasShrugged]

[djkeev]

I'll quote member kourt from an earlier thread.......

[flameisley]

Great info! Thank you everyone.

[Vantropy]

Just added a Small Car auto trans cooler.

Before the install, I measured the ATF (operating temp, idling, level) and it was high.

Only lost about 3-4oz of ATF in the cooler process, so thought it might bring it down where it should be. Drove for 5 minutes, found things weren’t tight enough & were leaking. Got back, checked ATF (operating temp, idling, level) and it was quite low, just at the tip of the dipstick. Added about 6oz of ATF. Called it a night.

Next day, I check the dipstick cold after settling, looking for it to be near the tip of the dipstick again. Instead, it’s overfull. I’m wondering if after filling, the engine needs to be idled a minute to settle the ATF? Or did I just add too much?
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1989 2.1L Vanagon Westy, Automatic, Titian Red

[SCM]

I'm convinced that measuring the ATF is a mysterious black art sort of thing.

Mine always appears too high, even after I got it back from being rebuilt and installed by a pro. It seems to work fine so I just monitor it to make sure the level hasn't changed.

Question: if you haven't driven the van far enough to be adequately warm, would you expect the ATF level to read higher or lower than it would if you drove the correct number of miles prior to measuring?
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'91 Westfalia GL Automatic (GTA "Turbo" Rebuild w/Peloquin) and 2.3L GoWesty Engine

[Vantropy]

[Wildthings]

The reason you check the ATF hot and running is that that is the standard. Checking it cold and/or not running is pretty meaningless especially if your system is no longer stock, as per yours with an added cooler.

[Vantropy]

[Vantropy]

kourt's advice above to check fluid after driving 10 miles is worth noting. Everywhere I see that this test should be done "at operating temperature," and you might think that this is when the engine gets up to operating temperature.

But the truth is that the transmission takes longer to warm up than the engine. Like: twice as long. Once I got my gauge hooked up, I kept thinking I had a problem, that the gauge wasn't working. But I had only been driving a couple miles and it hadn't even registered past 100 degrees. After ten minutes of driving, it's up to a stable 150 degrees.

And at that point, I take get my ATF measurement correctly.

And yes, when the engine cools down, the dipstick reads high still. So I can conclude that after adding a transmission cooler, there will be a higher cold reading than stock. I'm guessing this is due to the volume of fluid that is in the hoses above the fittings draining down into the pan.
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1989 2.1L Vanagon Westy, Automatic, Titian Red

[Butcher]

Most of the heat developed in an automatic transmission is from the torque converter. It's really not working while in park. That is why you need to drive the vehicle for several miles. Freeway driving seems to be the fastest.

[MarkWard]

You don't want the fluid draining out of the hoses. That means everytime you start the engine, the air will need to be purged from the system before you reach system pressure. I would confirm that is what is happening.

[Vantropy]

[tencentlife]

After sitting awhile and starting cold, you have to put the auto-trans briefly into every gear for a couple seconds while holding the brake, then put it in Park and only then can you expect an accurate fluid level reading. Fluid in the valve body and control passages will drain down over time and raise the fluid level, a lot. Running the engine and putting it briefly into each gear fills all the internals of the trans and it is only in that condition, plus the fluid being at operating temp, where you can get an accurate level reading. There's a pretty narrow range of volume allowed, overfilling will damage the trans as well as running low, so auto-trans fluid checking is considerably more stringent than an engine or manual trans. Observe the steps specified on the Bentley page copied above, follow every one.

Your external oil cooler will also be filled by doing this, just as the stock one would, making the question as to whether or not it also drains down moot.

Checking level without the engine running tells you nothing of value, except that there is some oil in the thing. Any time you check level on a cold auto-trans that has been sitting for hours, you should expect it to read well above the Max mark before the engine is started, then after starting and putting it in each gear, then in Park, if filled correctly it should read at about the cold or Min mark, then at operating temp it should read at the Max mark. The last one is the one that matters.

And yes, warming the engine up without driving won't warm up the trans, it has to be driven for some time, the page above states 6mi. (10km).
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[Vantropy]

[jlrftype7]

[Wildthings]

[Vantropy]