ATF: Which is worse, 1 quart high or one quart low?

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Oct 18, 2021
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We have a 1995 Chevy C2500 pickup 5.7L with a remanufactured engine installed last winter due to a catastrophic oil leak. A bushing in the front of the transmission was replaced while the engine was out, and the rear transmission/differential was overhauled in 2019 (I know very little about transmissions, so please excuse any lack of correct terminology). Yesterday, my husband noticed a tap-tapping or ticktickticking noise and decided to add quart of automatic transmission fluid without checking the level first. He said the truck ran much smoother and felt more powerful after that, but I'm an overcontrolling wife, so I checked the fluid levels and found a) ENGINE oil was down 2 quarts, and b) TRANSMISSION fluid was overfilled beyond the crook in the dipstick with the engine about 160 degrees F and running.

So, I headed to Harbor Freight for one of those siphon pumps and after topping off the engine oil I sucked out ATF (with engine off) through the dipstick tube until it seemed like about a quart, but the dipstick was still showing overfilled, which didn't seem right, but I sucked out some more anyway. Then I had my husband turn on the engine and go through the gears, and now of course nothing showing on the dipstick at all. So I added some Dexron VI, but it seemed like I had to add a lot and next thing it's looking overfilled again, plus now the gear selection lever is loose and doesn't shift anything any more. After YouTubing and with my husband's description of what he felt as he was changing the gears, I suspect the shift cable/linkage/bushing up near the steering column has failed with all of this gear changing after 26 years and several hundred thousand miles of nothing but Park-Reverse-Neutral-Drive. Nice little complication, that.

So, now while I wait for my husband to make arrangements with the IID monitoring company so we can have the truck towed to the stealership get fixed (it needs some other unrelated work as well), I actually measured how much ATF I moved. I have in the oil collection pan approx 1 quart + 3 cups that I removed from the transmission at the beginning, and I put back about 1 quart plus 9 oz of fresh ATF. So now it's overfilled by about a pint, assuming it was correctly filled in the first place.

Should I have just left well enough alone? Should I go back and remove another pint of ATF, or have the dealership adjust the level while the truck is there anyway? Generally speaking, which is worse, one quart low, or one quart high?

Thanks,

Rebeccah
 
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I've found ATF measurements to be unnecessarily difficult and been in a similar situation. It just requires multiple attempts, a lot of time, careful measuring and recording, and patience. Take out some, run, row gears, measure carefully, record it, and repeat until you can get in the correct zone.

I'd say neither over or underfilling is good...

One suggestion is to learn what the correct full empty amount is (e.g. manual might say a full drain is 4L), and start over by by draining and filling that entire amount to try to get to a known baseline per the manual. But that's not a great solution as manuals are sometimes incorrect or off by a not insignificant amount. But it's an option if the manual is reliable.
 
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I change fluid when the fluid is COLD / COOL in outdoor temps of mid 50s' to low 70 . That way comparable to the temp of the bottled A.T.F. stored
indoors . Will use HOLT 2.3 Gallon Manual fluid extractor when tranny fluid is cold or just drive onto ramps and shut off the engine so not much expansion of the fluid . Usually works with matching level of removed fluid .
 
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On any older American truck the ATF is to be checked with the engine running. Dipstick will show overfilled with the engine off.

There are usually some notes about checking procedures stamped on the dipstick, and of course as someone else said consult the owner's manual.
 

Rebeccah

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Oct 18, 2021
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On any older American truck the ATF is to be checked with the engine running. Dipstick will show overfilled with the engine off.

There are usually some notes about checking procedures stamped on the dipstick, and of course as someone else said consult the owner's manual.
I knew it was supposed to be checked with the engine running, didn't know that it would show overfilled with the engine off (saw that on another forum as I was searching around after the fact), but suspected it when the level didn't continue to go down after I thought I had sucked out what hubby put in.

If the shift linkage hadn't failed, I would have continued titrating and checking level with engine running.
 

Rebeccah

Thread starter
Joined
Oct 18, 2021
Messages
4
Ye
I've found ATF measurements to be unnecessarily difficult and been in a similar situation. It just requires multiple attempts, a lot of time, careful measuring and recording, and patience. Take out some, run, row gears, measure carefully, record it, and repeat until you can get in the correct zone.

I'd say neither over or underfilling is good...

One suggestion is to learn what the correct full empty amount is (e.g. manual might say a full drain is 4L), and start over by by draining and filling that entire amount to try to get to a known baseline per the manual. But that's not a great solution as manuals are sometimes incorrect or off by a not insignificant amount. But it's an option if the manual is reliable.
Yeah, I wish we hadn't lost the ability to change gears mid way through the process. We don't have a lift and I'm not dropping any transmission pans, so while I understand the concept of draining and filling to "start over", I won't be doing it. My "start over" would be to have a pro do it.

I'm more into DIY than the average female (or even the average male, I guess), but I wouldn't even consider myself a hobbyist. If it looks easy on YouTube and I think I can avoid causing more damage/chasing one no-longer-readily-available part after another/crawling underneath the engine and getting covered with black filth or oil, I'll often give it a go. I used to do my own oil changes several decades and about 50 lbs ago (changed the oil pan on my VW Rabbit, too), but the last time I did an oil change was just gross and not a significant cost savings nor an interesting learning experience. So I don't do that any more.
 
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Welcome 🎉

Being too high is worse than being too low

If it's too low, you can always add more, while it's harder to remove excess :unsure:
 
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Ye

Yeah, I wish we hadn't lost the ability to change gears mid way through the process. We don't have a lift and I'm not dropping any transmission pans, so while I understand the concept of draining and filling to "start over", I won't be doing it. My "start over" would be to have a pro do it.

I'm more into DIY than the average female (or even the average male, I guess), but I wouldn't even consider myself a hobbyist. If it looks easy on YouTube and I think I can avoid causing more damage/chasing one no-longer-readily-available part after another/crawling underneath the engine and getting covered with black filth or oil, I'll often give it a go. I used to do my own oil changes several decades and about 50 lbs ago (changed the oil pan on my VW Rabbit, too), but the last time I did an oil change was just gross and not a significant cost savings nor an interesting learning experience. So I don't do that any more.

No harm in knowing your limitations. I just had to have my car towed to the auto shop. I tried doing some work, and royally screwed something up. So, it's now at the shop to fix my screwups.

It's a learning process, experience, etc. DO what you can, and know your limits and call in pros when needed.

Transmissions are important and if you cannot do it right, get the pros.
 
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virginia
If I had to choose which I'd live with it would be one quart over. Why, because heat is the #1 destroyer of transmissions and for that reason I don't want reduced capacity. I'm not sure of the ill effects of too much but I've overfilled about a quart and didn't want to go thru the hassle of fixing it (no drain plug, dip stick too long to siphon) with no known I'll effects.
 
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We have a 1995 Chevy C2500 pickup 5.7L with a remanufactured engine installed last winter due to a catastrophic oil leak. A bushing in the front of the transmission was replaced while the engine was out, and the rear transmission/differential was overhauled in 2019 (I know very little about transmissions, so please excuse any lack of correct terminology). Yesterday, my husband noticed a tap-tapping or ticktickticking noise and decided to add quart of automatic transmission fluid without checking the level first. He said the truck ran much smoother and felt more powerful after that, but I'm an overcontrolling wife, so I checked the fluid levels and found a) ENGINE oil was down 2 quarts, and b) TRANSMISSION fluid was overfilled beyond the crook in the dipstick with the engine about 160 degrees F and running.

So, I headed to Harbor Freight for one of those siphon pumps and after topping off the engine oil I sucked out ATF (with engine off) through the dipstick tube until it seemed like about a quart, but the dipstick was still showing overfilled, which didn't seem right, but I sucked out some more anyway. Then I had my husband turn on the engine and go through the gears, and now of course nothing showing on the dipstick at all. So I added some Dexron VI, but it seemed like I had to add a lot and next thing it's looking overfilled again, plus now the gear selection lever is loose and doesn't shift anything any more. After YouTubing and with my husband's description of what he felt as he was changing the gears, I suspect the shift cable/linkage/bushing up near the steering column has failed with all of this gear changing after 26 years and several hundred thousand miles of nothing but Park-Reverse-Neutral-Drive. Nice little complication, that.

So, now while I wait for my husband to make arrangements with the IID monitoring company so we can have the truck towed to the stealership get fixed (it needs some other unrelated work as well), I actually measured how much ATF I moved. I have in the oil collection pan approx 1 quart + 3 cups that I removed from the transmission at the beginning, and I put back about 1 quart plus 9 oz of fresh ATF. So now it's overfilled by about a pint, assuming it was correctly filled in the first place.

Should I have just left well enough alone? Should I go back and remove another pint of ATF, or have the dealership adjust the level while the truck is there anyway? Generally speaking, which is worse, one quart low, or one quart high?

Thanks,

Rebeccah
If the transmission behaves itself one quart over it's probably okay. Under filling could burn up the fluid.
 
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One quart below the full mark is usually okay on most dipsticks, still falls within the safe range. One quart say over the full mark, I would drain that quart for sure.
 
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How do you know if it's being churned and foaming or not?
If you have a dipstick pull it out with the engine running, if it's covered in bubbles or froth then it's foaming. I would also doubt the transmission would shift properly since it requires hydraulic pressure that can't be achieved with air entrapment.
 
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I wouldn’t be comfortable with a quart overfilled, but half a quart I could live with, especially on an older vehicle whose transmissions were designed for DIY service.

Nowadays most new vehicles lack dipsticks and fluid had to be checked at a specific temperature and aren’t as accommodating to varying fill levels.
 
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