How Much Does ATF Expand With Heat?

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8
Location
AZ
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Howdy, I always wondered why ATF must be checked at a certain temperature range and figure it must expand quite a bit. Old dip stick method had a ~2" of variance. My new Tundra uses the "open valve" method like a differential but needs to be in a specific temperature range that makes it a PITA compared to dip stick although more accurate.. So if I have a 15 qt capacity how much would it measure at 50°F vs 120° F ? As temperature rises does it expand more? Does it even expand or need to be thin enough to fully immerse all the little ports and be flowing fully? Thanks
 
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3,922
Location
SW Ohio
I can only relate my experience and it's this: On 3 separate occasions, I drained between 3.5 and 4 quarts of ATF from two different vehicles. Did this while the ATF was "hot", in excess of 150º F (after a good 30 minute drive). Poured it into a container and marked the level. Using an infrared thermometer and waiting close to an hour, it eventually dropped to around 75-80º F and for all practical purposes, the level did <span style="font-weight: bold">not</span> change. Certainly not enough to visually notice.
 
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34,425
Location
NY
Here's a picture for the NAG 1 transmission fluid level graph. You can get an idea of how much the ATF used for that unit [ATF+4] expands and take an educated guess based on that. [Linked Image]
 
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1,654
Location
Prospect, KY
Quote below hope it helps: Link: https://www.dieselplace.com/forum/5...llison-fluids-engineer-here-help-29.html -------------------------------------------------------------------------------------------------------------------------------------------- Coefficient of thermal expansion for oils and transmission fluids is around 0.0007 per degree C (0.07%/C). So, if you've got 12 liters in the pan, it will expand 0.0084 L per degree C. Since there's increased volume, and the surface area of the fluid does not change appreciably, the fluid goes higher on the dipstick. Volume = Area x Height. So, Height = Volume/Area. Therefore, height on the dipstick is proportional to volume change. Summer time temperature change might be ambient air temperature 68F (20C), at start up, to around 180F(82C) at operating temperature. Or, around 62C. Therefore, during the summertime, the fluid could be expected to expand 0.0007 x 62C = 0.0434 (4.3%). Share
 
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