I didn't mean below bottom line.
Are we over exaggerating the perfect ATF fluid level? thermal expansion seems to think we are
- Thread starter apollo18
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If your transmission is not leaking and is performing as intended and the transmission is at ambient temp and as stated in previous posts vehicle is level and tyres are correct pressure, I cannot see any issue.
The amount of fluid removed will be the same volume as the replacement fluid, the fluid can be weighed but in the absent of any meaningful data I would not be concerned about the small if any difference between volume and weight in this situation.
If a person cannot find a level area for an ATF change, then how does one check their engine oil level.
Many vehicle manufactures have very hit and miss methods of checking fluid level, it is an opinion what a slow stream, or drippling of fluid means to different people when trying to determine the correct level. I am only referring to sealed transmissions (no dip stick) however dipstick transmissions still require a level area for correct checking of the fluid level.
The amount of fluid removed will be the same volume as the replacement fluid, the fluid can be weighed but in the absent of any meaningful data I would not be concerned about the small if any difference between volume and weight in this situation.
If a person cannot find a level area for an ATF change, then how does one check their engine oil level.
Many vehicle manufactures have very hit and miss methods of checking fluid level, it is an opinion what a slow stream, or drippling of fluid means to different people when trying to determine the correct level. I am only referring to sealed transmissions (no dip stick) however dipstick transmissions still require a level area for correct checking of the fluid level.
Doing all this is "simple"- instead of just a dipstick? Really...
I have three transmission types - AW-55 in the Volvos. NAG-1 in the Mercedes. AB-60F. All three require a specific temperature at which the level is checked. I’m familiar with all three. The cars all get the fluid changed regularly.
The Volvos have a dispstick.
The Mercedes are sealed, but have a “service tool” that is a dipstick.
The Toyota has the second plug.
Of the three procedures, the second plug is the quickest.
The simplest.
And it is unambiguous. Set it and done. No inserting dipstick, twice, to wipe the fluid off that is still in the tube from filling, and checking the temperature, then figuring out how much to add, or vacuum out, adding/subtracting fluid, then checking again with the dipstick, and perhaps another iteration of add/vacuum.
You are very meticulous and knowledgeable but I don't think transmissions are That sensitive to fluid levels. Just keep it between the add and full marks IMO
You are absolutely right that I am meticulous, but that's what I am saying. "just between the add and full marks" is exactly what I am doing. Nothing more.
To get the Volvo right, between the full and add marks, is +/- 100ml at the proper temperature. That takes a couple of iterations, after the car is at temperature, idling, and in gear.
The MB is more tolerant, with a wider range between full and add, but it still can take a couple of iterations.
The second plug method is quick: one, and done. When it's set, it's set, you don't have to go back, add or subtract fluid, and recheck.
Wait until temp is achieved, pull the plug, let it drain. Close it up. Done. No recheck. No worries.
Of all the automatics, this is the simplest and quickest to get right after a fluid change.
Yes, you are right. This has been covered before on BITOG. SPK2000 in an Oct13, 2019 post calculated (using thermal coef of ATF) the volume change in ATF going from room temp of 68F to operating temp of 180F as 4.3%. Anywhere in this range probably gets you really close. IMO, this is negligible for all this effort (Iterations, waiting, subtract, add, drain, dribble)
Again - I think you're completely missing my point.
The drain and dribble is far easier than the dipstick.
It is just that simple.
Faster, easier, more accurate.
But because everyone has experience with the dipstick, they think drain and dribble is hard - but it is not, it is easy.
I like it better. Faster, easier, more accurate.
Now, your 4.3% math? Eh, then why does it raise the level in the NAG-1 by over 3cm?
It's not total fluid volume that counts in a transmission, it's the level of the fluid. Too low, the pump sucks air. Too high, it gets whipped into foam by rotating parts.
The volume of the preponderance of the fluid is largely constrained (internal parts, plumbing, cooler, etc. stay the same size) so all of the fluid expansion all takes place in the volume above the pan.
Further, folks are making the assumption that only the pan volume is expanding, but it is the total volume of the fluid that is expanding, so, 10 liters in the the case of my Toyota. Or Mercedes. Big difference in where your 4.3% goes.
That total expansion takes place only in the volume above the pan. That part of the transmission, that volume, is impinged/constrained by the valve body, and castings, so the level, as measured from the bottom of the pan, DOUBLES between cold and hot (that is 20C - 80C) in the case of the NAG-1. That's not a small amount. That's huge - and all from your calculated 4.3%. The volume into which the fluid expands is not the area of the pan, it is some small fraction of that area, because that area is taken up by the valve body and other parts.
The proper level is greatly affected by total fluid volume and it is level that matters. The operating level, inn the case of the NAG-1, changes by 100% because of those factors. That is why the difference between the top and bottom of the range in the Volvo AW-55 is only 200ml. Because the volume into which the fluid can expand, at that level, is quite small, and the quantity of fluid that is exanding, si the total fluid in the transmission.
So, getting the level correct is what ensures that the transmission operates properly.
And that is most easily done with a drain and dribble set up, like the Toyota.
I’ve read about several cases of the 10r80 in Mustangs causing erratic shifting behavior.
The 10r80 in a friends F150 was about 1/2 quart low at full operating temperature, although it didn’t seem to cause any problems.
Regarding the fluid quantity between cold and hot, I was only able to see about an 8-10 oz difference between the being at 100 degrees vs just over 200.
To the Toyota techs, can u briefly outline the procedures for a flush and transmission filter change? Do u 1st drop the pan, change the filter, flush for a clean color and then fill with the intent to drain at the correct temperature?
yeah even with the math and just eye balling a number 10oz of expansion for 100 degrees sounds about right
I think it’s all relative to the capacity of the unit and what kind of fluid. Some of the D6 dozers we have hold about 40 gallons or so of 30 wt trans oil. The difference between ‘hot add’ and ‘hot full’ is about 10 gallons.
Say what you will about Chryslers and their transmissions, but their fluid level chart is very good. Well at least for the 62te tranny, I don’t know the other ones.
Plenty of temperature points to choose from as well as clearly defined range of fluid level.
Plenty of temperature points to choose from as well as clearly defined range of fluid level.
Would be cool if we could convert fluid level to quarts of total fluid
You never will.
Because the rate at which the fluid drains from various actuators, valve passages, and accumulators within the transmission varies.
So when you drain it, hot or cold, and how long it’s been open or how long it sat before it drained, all affect the amount of fluid that has returned the pan, and the net result is that you get a different amount out nearly every time.
It’s not simple, like an engine. I’ve got the ATRA rebuilders manuals for both AW-55, and the NAG-1.
The amount of fluid, the stated capacity, for the transmission is an approximation.
Again, it’s the level that matters, not the number of quarts in the transmission. The relationship between the level of fluid, and the pick up, as well as that fluids proximity to rotating parts, is what determines whether or not the pump drawer, or the fluid gets whipped into foam.
The levels shown on a dipstick, or set with a tube, are designed to keep both of those things from happening.
Here's how I learned that the temperature and level check procedure matters
I drained my Touareg while hot, and measured the ATF. I put in the same amount of ambient ATF.
I had to do the level check procedure 3 times, it was so overfilled.
Now I drain at ambient, measure at ambient, and fill at ambient. When the trans is up to temp I pull the plug and it's right on the money.
If you have an accurate scale and you know that the level in your transmission is properly set (no leaks, not under or overfilled, etc.), measuring by weight is probably the most accurate and fastest way to get the same back in that came out.
I drained my Touareg while hot, and measured the ATF. I put in the same amount of ambient ATF.
I had to do the level check procedure 3 times, it was so overfilled.
Now I drain at ambient, measure at ambient, and fill at ambient. When the trans is up to temp I pull the plug and it's right on the money.
If you have an accurate scale and you know that the level in your transmission is properly set (no leaks, not under or overfilled, etc.), measuring by weight is probably the most accurate and fastest way to get the same back in that came out.
How long does it take for the transmission fluid to get down to ambient temp in your experience?
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My kids Toyota wasn't all that hard, 1st Toyota we serviced. We measured cold, added back about the same, warmed it up, added a bit more until it started draining and let it slow. Pretty easy actually but I don't think a bit over/under is going to hurt. Only thing I really didn't like about it was the up and down under the truck more than a dipstick. My kid did all that and I just filled from a hose up top we ran, easy for me anyway.
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