ATF D/F, hot, warm, or cold ?

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I've seen reasons from people saying to drain ATF when it's hot, others say do it when it's "warmed up", and others say to do it when it's cold (let the car sit overnight and drain in the morning, for example). Varying reasons are when hot, it flows better. Or when it's cold, any 'sediment' should have settled to the bottom of the pan and come out (vs getting 'caught' in different parts of the transmission before it's dropped down ?).

Finally, at least with a D/F, ATF expands when warm/hot so the amount you measure isn't accurate when you replace it with the same amount of COLD ATF (you'll put in (slightly) too much). I realize one option is to let it drain and cool down and then use that measurement amount. If so, to what temperature - ambient (same temperature as the new ATF that's sitting waiting to be used), 100º F, 125º F ?
 
You are supposed to check/ add ATF to a hot transmission.

Say 4 hot quarts drain out and 4 cold quarts are dumped back in... I personally don't think that'd even be enough to matter. Heck, there may even be more user error in the measuring and adding.
 
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I just left the bottle out overnight after getting the car into a position where I could service it.

One thing I have considered is if your fluid is contaminated, would the contaminants make a difference in the volume of fluid versus clean fluid? When I changed my ATF it was black as coal, and the on the second D&F it was black with a reddish tinge. Surely that fluid had less ATF per unit of volume than virgin ATF?
 
Originally Posted By: hallstevenson
I've seen reasons from people saying to drain ATF when it's hot, others say do it when it's "warmed up", and others say to do it when it's cold (let the car sit overnight and drain in the morning, for example). Varying reasons are when hot, it flows better. Or when it's cold, any 'sediment' should have settled to the bottom of the pan and come out (vs getting 'caught' in different parts of the transmission before it's dropped down ?).


Actually if you wait for the fluid to cool off and allow the sediment to settle, it's actually WORSE because that's when the stuff gets stuck behind. Every flush manufacturer show the same thing. Here's some pics.

I recommend you change it Warm, so you don't burn yourself while working on the car. This way all the contaminants are suspended and COME OUT with the OLD OIL. This should be common sense.



 
A fellow claimed he'd pull the plug for a D&F then chase out whatever drained with one fresh quart of fluid.
His idea was to rinse out the bits depicted above.

Seemed wasteful to me.

I like the idea of positioning the car the night before (in my case, on ramps)....but I don't do it.
 
Originally Posted By: Kira
A fellow claimed he'd pull the plug for a D&F then chase out whatever drained with one fresh quart of fluid.
His idea was to rinse out the bits depicted above.

Seemed wasteful to me.

I like the idea of positioning the car the night before (in my case, on ramps)....but I don't do it.


Our 2017 Explorer with the 6F35 transmission does not have a transmission dip stick, but an easy to access fill tube. So if I want to change it myself, because it's sooo easy to do and inexpensive, I I drive it up on the ramps the night before and change it the next morning. That way the temp of the ATF drained is the same as the temp of new fill ATF. I'm going to change it more often, because it's easy and cheap to do, hopefully I don't have to worry about build up in the base of the pan. We purchased the Explorer new and did the first drain and fill at 12,200 miles.

Whimsey
 
I like to drain lukewarm or warm. Then I set the fluid level to the cold range, go out on a 15-20 mile drive to get the tranny to operating temp and do a check after running the gears and idling. However, if the car had no dipstick I’ll check the temp within OEM specs.
 
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Originally Posted By: dlundblad
You are supposed to check/ add ATF to a hot transmission.

Say 4 hot quarts drain out and 4 cold quarts are dumped back in... I personally don't think that'd even be enough to matter. Heck, there may even be more user error in the measuring and adding.


This is why I do it cold. Plus the not burning yourself thing
 
So the consensus is, do it hot or warm or cold....
grin.gif
 
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