Are we over exaggerating the perfect ATF fluid level? thermal expansion seems to think we are

[webfors]

This is why I intend to do mine by weight, with a very precise scale. Measure the empty pan, measure the full pan, scale as I pour fresh fluid in. Temperature won't matter. Mine has never been opened, factory fill from Japan, so I am assuming they got it correct.

However a tech here told me they did by volume, and I believe him. The "till it stops dripping" is not only 100% dependant on temp, but level - and how on earth do you know a used vehicle is level given the transmission is sprung weight and springs settle unevenly? It is such an issue Toyota issued a TSB, and some new tools - see video below - I cued it to the proper part but starts around 7:00. Anyway, I am sticking with weight, or really, mass.

Be great to have that Toyota adjustable tool that allows you to check at any temp!

 

[Jeep_Riot]

A Toyota tech on this board told me they do it by measuring what came out. I plan on weighing mine when I get around to it.

What if the vehicle was low on fluid? You’d be back to being low on fluid. The only difference is it’s new fluid.

Now sure this works for me…

 

[meep]

I screwed up the Toyota method once, I think. It was a GS350 purchased used with something like 80k on it. The fluid came out pretty bad, so once it stopped dripping, I started the car a couple of times for 20 seconds or so, which burped a little more fluid out, probably another quart, maybe even a quart and a half (that will likely generate another debate here, it’s at idle, under no load, no clutches engaged, and theres still 3+ quarts of fluid pumping around if it’s a smaller unit).

Following the standard Toyota DIY procedure with a tactile fluid temperature sensor (my gloved hand), I thought I heard an odd “aeration” noise on the test drive. Went back, let it sit, added more, again the ‘yota DIY, and it was good.

Thats the only time I’ve missed.

The way these drain, it’s a full wide stream as long as the drain tube is fully covered in fluid. When it’s no longer fully covered, the stream changes into something that kind changes shape as it drains. I know it’s close when that happens. When that stream cuts to about half width, I stick the Allen bolt back in.

 

[Sumboodie]

Seems wild the sight hole isn't at normal "cold" like most any other fluid level.
If I go fill a gearbox or final drive, fill till it comes out and it's good.

I haven't kept up with these new whizz bang transmissions, but most before could be low a quart or two (depending on pan size)and still function just fine.

This thing here sounds like if it's off by 4 drips the sky will fall

 

[webfors]

Just did check level after three dump and fills and this is what I did on the 2014 ATS 6 speed. YMMV.

1. Brought a big fan to the lift
2. Opened the hood and put the fan under the car to push the heat out.
3. While it was cooling down I performed the final dump and fill.
4. I pumped new Dexron VI fluid until it came out the fill hole and plugged the fill hole. That’s about 400-500ml overfilled from my experience. Why? More new mixed in fluid before check level dump.
5. Got the TFT to 104f with the fan and car off.
6. Started the car, shifted through the gears, then left running in park.
7. Lifted the car back up and pulled the check level plug.
8. About 500ml came out (did not measure, because there’s no need)
9. Put the plug in once it started to trickle/dribble/drool whatever. Stream changed from flow to inconsistent dribble Drabble.
10. Max temp was 113f, which is in range.

With that procedure I don’t need to measure or weigh anything. The procedure does it for me.

 

[webfors]

I think OP is bang on if we’re talking a small spread of temps like 10-15 degrees. But it is interesting that even GM’s procedure allows for an almost 40 degree range.

 

[D1dad]

Just did check level after three dump and fills and this is what I did on the 2014 ATS 6 speed. YMMV.

1. Brought a big fan to the lift
2. Opened the hood and put the fan under the car to push the heat out.
3. While it was cooling down I performed the final dump and fill.
4. I pumped new Dexron VI fluid until it came out the fill hole and plugged the fill hole. That’s about 400-500ml overfilled from my experience. Why? More new mixed in fluid before check level dump.
5. Got the TFT to 104f with the fan and car off.
6. Started the car, shifted through the gears, then left running in park.
7. Lifted the car back up and pulled the check level plug.
8. About 500ml came out (did not measure, because there’s no need)
9. Put the plug in once it started to trickle/dribble/drool whatever. Stream changed from flow to inconsistent dribble Drabble.
10. Max temp was 113f, which is in range.

With that procedure I don’t need to measure or weigh anything. The procedure does it for me.

View attachment 279903View attachment 279904

I use that guage as well. Nissan says max drain temp is 105 and I noticed the guage is a few seconds behind so I won’t go past 103. Once all my cars were set, I just use a couple of gallon jugs from the dollar store and a cheap digital meat thermometer. Once both fluid temps are the same, I put in what came out. A few hundred K and never an issue on my 3 cars. I wish I had a lift as I’m getting to old to slide around lol.

 

[Dragfluid]

hello, i recently changed the atf fluid in my 2015 toyota. it has the u760 tranny and the u760/u660 have no dipstick so they have a certain level check that happens between 104f-113f and some docs say the fluid check can be done between 95-113f. The drain hole/port has a little fill tube preinstalled to do the fluid check. When the temp is around 104f, the instructions say to take out the drain plug and to drain and word for word based on the toyota document "Wait until the fluid flow slows and only drips come out"

depending on how much fluid comes out, a tranny could easily be at 115-120f when only drips come out. Also everyone has a different definition of 'only drips come out". I watched many youtube videos of people doing the fluid check and people were reinstalling the drain plug when the fluid was still draining as a slight stream, dribbling, and or dripping at a super slow speed. All in all it doesn't seem like anyone experienced any ill fate based on what they defined "a few drips come out" as

when i did my level check, idk how perfect i got it as i started dumping fluid out of the hole at around 104f and not sure what the temp was at when only a few drips came out. I probably reinstalled the plug within 30 seconds and when I did reinstall it, I was definetly closer to the "few drips coming out"

Of course I was planning to recheck the fluid in a few days which is why I didn't do a perfect level check the first time however all of this got me thinking.

I started wondering to myself on how much the fluid could even expand between the 104f to 113f and even if someone stopped the fluid level check at 120f how much extra fluid could even be drained/how 'off' the fluid level check could be. So I pulled up google and started looking for the thermal expansion of ATF which seems to be around 0.07% per delta degree celcius. So I decided to put some math into it and lets see what we come to. Just incase the 0.07% is too low, lets just round that value to 0.1% per delta degree celcius just so we can have the safest value incase 0.07 is not correct.

Toyota says the fluid level should be set at 104f to 113f. Which essentially means they give a 9F window to do the level check meaning even if you set it perfect right at 104F then that is the same as someone else who set it perfectly at 113F even tho both will have a slight variance in total fluid level in the system

Assuming most people probably reinstall the plug too late rather then too early (too much fluid is coming out and temperature heats up before plug can be installed)

For our example lets say a perfect fluid level check is at the average of 104f to 113F. so lets say the avg is 109F. Lets also assume 'Joe' ends up finishing the fluid level check procedure at 120F. (i seriously doubt someone could take longer then 1-2 minutes setting the fluid level as long as they started to take the plug out at around 100F. Lets also say the whole tranny and tubing/cooler line system holds a total of 10 quarts. (the tranny/tq converter holds about 6q from a dry fill so lets say 4q more for the cooler and the remaining tubing)

109F = 42.77 Celcius, 120F = 48.88 Celcius.
The delta of these two also known as the change in these two would be : 48.88C - 42.77C = 6.11 Celcius.

0.1% / 100 = 0.001 (to get rid of the percent). 0.001 / Degree C x 10 Quarts capacity x 6.11 C = 0.0611 quart expansion when starting at 109F and ending at 120F

Now lets expand that quart decimal and see what we get in ounces/Ml.

1 Quart is 946mL or 32 oz. Which means that 0.0611 quart is equal to 57.8mL or 1.96 oz

So essentially the fluid level in the whole system would only change by approx 2oz or 2 table spoons between 109F and 120F
which in other words means someone who set the level perfectly at 109F would have 2 tbsp/2oz more fluid then someone who incorrectly set it perfectly at 120F

Now this is where the discussion begins. I am not a tranny mechanic or a tranny engineer. But what I think is that there is no way that someone incorrectly setting the fluid level as described above could end up doing any damage to there tranny. 2 tbps or 2 oz is the smallest amount. Could a system that holds 10quarts of capacity really be bothered with a variance of 60mL? that seems like the tinyiest amount. HOWEVER i totally agree that someone setting the fluid level incorrectly and having 1quart under or 1 quart over is probably not doing there tranny a favor. I am in no way saying not to ignore your certain tranny fluid level check procedure. All I am trying to say is as long as you are in the ball park range of setting the fluid level on your tranny I doubt you can do any damage. I have spoken to many mechanics and alot of them just measure what came out and refill that much in and they seem to never have any problem and now that I got the math into it it totally makes sense. It seems like the only way people can do damage to there tranny or will have symptoms of wrong fluid level is if they are a considerable amount of fluid low or high. Maybe that value is a pint, maybe that value is 1 quart. I don't really know but I seriously doubt anything less then 100mL could do any damage.

I also believe that the reason these brands have a stingent fluid level check procedure is for the people who want it to be perfect and also so that most people are in the ballpark range. If they had no dipstick and no fluid level check procedure then people could easily be 1-2 quarts over or 1-2 quarts too less. So by following there fluid level check procedure, even if you don't finish it between there outlined temp range of 104f to 113F as long as you did it close enough to that temp range you are probably safe. I am not saying to do the fluid level check at 200F and assuming it will be the same as 104F, no way it will be. However as long as you finish the fluid level check at 120F or even 95F you are probably FINE since the variance between the perfect fluid level as per Toyota and being off by a few degree celcius / F can only really change the total fluid level in the system by maybe 1 tbps, 2 tbps, 3 tbps or 1oz, 2 oz, 3oz, etc


However I opened this thread as a discussion and hope to hear some knowledgable info about this, maybe I am completely wrong and that tranny's want there fluid level to be precise to the t and cannot tolerance a fluid level variance of 2 tablespoons but with just imaging a drain pan and thinking 2oz are gonna make or a break a tranny seems impossible for me to understand. If I am mistaken please let me know so this thread does not end up educating DIYer's or mechanics in the wrong way

View attachment 214013

Saw this and though it's an old thread, I see that it's still active.
No, two ounces isn't going to make any difference. However there are some units where over filling significantly can cause overheating of the unit. Specifically, GM 6T40/45, Ford 6T35. It will get hot enough to melt plastic parts inside!

And I AM a TRANSMISSION mechanic. (retired)

 

[apollo18]

I think OP is bang on if we’re talking a small spread of temps like 10-15 degrees. But it is interesting that even GM’s procedure allows for an almost 40 degree range.

thank you, someone that agrees with me. if i had a graduated cylinder and something to heat with, i would do it

just need some atf and some heat in a graduated cylinder. semone heat it up to 100f and i bet the level barely increases. thats why we have calculations with in my original post shows the expansion is minimal