An interesting test regarding transmission fluid level readings measured at different ambient temps

[TJC]

So this morning I began taking ambient temps from inside the truck by simply turning the ignition on and recording the temp from inside the cab, them checking then checking the transmission fluid level. Here are my first two entries. The truck has not been started or moved. A 6F change in ambient temperature moved the fluid level up 1/2 a block on the dip stick. A bigger jump than I anticipated.

It reached a high of 66F today, but my garage remains colder longer. I'll keep updating this chart at spring progresses to quantify how ambient temps affect fluid level measurements.

It would be interesting if others could confirm my findings.

UPDATE: 4 May 2025
I am convinced that the rise in fluid levels is due to fluid draining from the transmission over time. I recently let my truck sit for 24 hours and removed 5 qts, Waited 24 hours and pulled another qt, repeated the process again and got another qt. The dropped the pan where another 0.5 qt was in the pan. Removing the filter resulted in more fluid.

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[Stevedbvik1]

Did you drive/ run the vehicle between tests. Or was it static the entire time? Transmission level will fluctuate cold due to drain back and how much the torque converter holds. Thats why they have you check it hot.

 

[TJC]

Did you drive/ run the vehicle between tests. Or was it static the entire time? Transmission level will fluctuate cold due to drain back and how much the torque converter holds. Thats why they have you check it hot.

I drove the truck 75 miles after the fluid change and parked it level for two days before beginning the static fluid level checks today.

The first check was made at 7am. The second made at 4pm. The truck was not moved or started.

I don't need the truck and will let it sit unstarted for all of the following checks as ambient temps climb.

 

[TJC]

Updated the chart this morning before the cold front comes through later today. Morning temp in the garage was 53F as measured from the inside of the truck on dash. Remember, I never start the truck, just hop in and turn the key to on long enough to get the temp, then check the fluid level with my MBS FitzStick.

Fluid level rose again this time to the bottom of the diamond in block 1. I am almost above the range of the dipstick, and will have to determine the best way to accurately report if the level continues to rise.

I have no explanation for the rise, but there are only three plausible possibilities that I can think of.

1. Fluid expanding as temps rise
2. Fluid still draining into the pan from upper areas of the transmission / torque converter
3. A combination of 1 and 2

Ambient air temp outside has been rising all night and is now 59F. Our high is forecast to be 62F. Storm front passes through by 1pm and temps will drop fast. Garage will moderate the change.

Our temps are dropping for the next few days. It will be interesting to see where the level goes from here.

BTW, It is very easy to see the fluid on the dip stick when it is stone cold! Nice and red. When hot I look more for the wet surface as the red fades as fluid thins out.

 

[KJRR]

I'm certainly no expert but would air pressure affect the level of the fluid?
May have more influence than a few degrees of temp.

 

[TJC]

I'm certainly no expert but would air pressure affect the level of the fluid?
May have more influence than a few degrees of temp.

Me either! Hadn't thought of that but it is certainly possible.

The fluid is now where I would have expected it to be when I first started checking. We'll see where it goes as temps rise and fall, and pressure changes. Pressure here is now 29.47in, but it is forecast to rise on Friday to 29.92in. Temps will still be cool at 54F / 33F for the high and low.

Garage temp will only change a few degrees though.

If pressure makes a significant difference, this should result in a lower reading... how much ? I have no idea, but we will know soon enough.

 

[TJC]

I'm certainly no expert but would air pressure affect the level of the fluid?
May have more influence than a few degrees of temp.

BTW, I LIKE your Ranger. Iconic Silver SCAB. Just like mine! It looks to be a Sport too.

 

[Rp930]

Maybe you should find a hobby.

 

[Fitzmotor]

Very interesting, is it the stock transmission pan or a aluminum aftermarket one?

I'm wondering about the volume effect.

I found this chart, not our transmission or fluid, but it's interesting. It really expands, 10 degrees really makes a difference.

 

[TJC]

I have lots of hobbies! Enjoy your day.

 

[KJRR]

BTW, I LIKE your Ranger. Iconic Silver SCAB. Just like mine! It looks to be a Sport too.

Yes Sport too. Not a lot of SCABs out there.
And I can think of a lot worse hobbies.

 

[TJC]

Very interesting, is it the stock transmission pan or a aluminum aftermarket one?

I'm wondering about the volume effect.

I found this chart, not our transmission or fluid, but it's interesting. It really expands, 10 degrees really makes a difference.

Fitz, Thank you for the input.

It is the stock pan. I have the PPE deep pan, but have not installed it yet. Waiting for the filter change.

I am really hoping to determine if a definable repeatable static (and accurate) filling procedure can be achieved. I currently do not have a way of measuring transmission temps. I've been very careful in putting in exactly what I take out. And since my transmission is now functioning properly I suspect that I will be changing the fluid often enough to warrant this effort. Probably every 10K miles. Won't know about that distance until I get there and see the transmission fluid.

It would be so much easier to simply fill to 6 quarts, start the truck long enough to allow fluid to flow throughout the unit, let it sit overnight, and top off to a given level when things have settled. This requires you change the fluid in the same place each time to insure the truck is level, and if temps don't matter this gets a lot easier. If they do matter, I'll have a nice table to use to set the level by.

I may be spitting in the wind, but won't know until I get a more diverse set of data measurements.

I don't like guessing.

 

[got3fords]

Maybe you should find a hobby.

THIS sounds like a hobby to me.

 

[got3fords]

I find this interesting. I like data. Although I am not sure what we are going to learn. Perhaps a way to make accurate and consistent static fluid level checks? Are you also recording pressure? I think that would be important.

 

[Grumpaw]

THIS sounds like a hobby to me.

This is not a hobby.....it is an obsession to find "Truth, Justice, and the American way" !!!
Like this pic of checking trans fluid.....

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