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

[TJC]

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.

I have the pressure numbers from yesterday and today, and will watch the pressure rise over the next couple of days to determine if the correlation is great enough to warrant monitoring it as well. I hope that it is not as that may be a bridge too far in complexity. I am looking for a heuristic, a rule of thumb in the 90th percentile of accuracy. If I am a 1/10th of a quart off I won't care.

But I have noticed that it doesn't take a lot of fluid to move the level up the dipstick once you are close. And that is what concerns me. I am looking for accuracy without measuring fluid temperatures at 206F to 215F.

I started thinking about this after watching the FordTechMakuloco video Ford 10R80 Ten Speed Transmission: Fluid and Filter Service Procedure

I followed his procedure as a test. My ambient temps were a 30F - 40F lower (My detached work garage is not climate controlled) than his heated garage, and I noticed my fluid level appeared low. This is what started my train of thought rolling.

Does his simple drain and fill 5-6 quarts, start the truck, shift through the gears at 10 second duration, then fill to the block below the target level specified in the manual hold true in significantly colder or warmer temperatures?

So now you have the back story.

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[got3fords]

I have the pressure numbers from yesterday and today, and will watch the pressure rise over the next couple of days to determine if the correlation is great enough to warrant monitoring it as well. I hope that it is not as that may be a bridge too far in complexity. I am looking for a heuristic, a rule of thumb in the 90th percentile of accuracy. If I am a 1/10th of a quart off I won't care.

But I have noticed that it doesn't take a lot of fluid to move the level up the dipstick once you are close. And that is what concerns me. I am looking for accuracy without measuring fluid temperatures at 206F to 215F.

I started thinking about this after watching the FordTechMakuloco video Ford 10R80 Ten Speed Transmission: Fluid and Filter Service Procedure

I followed his procedure as a test. My ambient temps were a 30F - 40F lower (My detached work garage is not climate controlled) than his heated garage, and I noticed my fluid level appeared low. This is what started my train of thought rolling.

Does his simple drain and fill 5-6 quarts, start the truck, shift through the gears at 10 second duration, then fill to the block below the target level specified in the manual hold true in significantly colder or warmer temperatures?

So now you have the back story.

I like it. Keep us posted. BTW, you can never have too much data. Even if you don't end up using it all in the end.

 

[RangerBill]

Fluids don't compress, so air pressure shouldn't affect level.

 

[Burnt Money]

I wonder if putting the Transmission fluid in a graduated cylinder and measuring if there are changes due to temperature would yield or pressure would yield any information? I haven’t read too deep into this thread but it’s definitely interesting!

 

[Grumpaw]

Fluids don't compress, so air pressure shouldn't affect level.

All real fluids are compressible, and almost all fluids expand when heated. Compression waves can propagate in most fluids: these are the familiar sound waves in the audible frequency range, and ultrasound at higher frequencies.

 

[TJC]

Just updated the chart with atmospheric pressure readings and my high temp reading for the day.

The cold front squall line is very close now so I took it early.. Very windy...

The fluid levels are even higher! Could the transmission still be draining into the pan? The reading is now well above the scale - about 3/16" above the top diamond.

Over 2 days Ambient Temps have climbed 10F and pressure has dropped substantially. Both correlate with the fluid rise.

 

[RangerBill]

All real fluids are compressible, and almost all fluids expand when heated. Compression waves can propagate in most fluids: these are the familiar sound waves in the audible frequency range, and ultrasound at higher frequencies.

If fluids can compress, then an engine wouldn't hydro lock when coolant leaks into a cylinder. Atmospheric pressure changes shouldn't make any difference in transmission fluid levels. Fluids do expand when heated, but I wasn't commenting on that.

 

[Stevedbvik1]

Just updated the chart with atmospheric pressure readings and my high temp reading for the day.

The cold front squall line is very close now so I took it early.. Very windy...

The fluid levels are even higher! Could the transmission still be draining into the pan? The reading is now well above the scale - about 3/16" above the top diamond.

Over 2 days Ambient Temps have climbed 10F and pressure has dropped substantially. Both correlate with the fluid rise.

I understand your quest. But I still think it’s a drainage thing. And could that be affected by temperature and or pressure also ? I’m guessing you would have to let it sit for a long time to let it all drain down. Maybe your test will establish that.

 

[Old Red Replacement]

The PPE pan has a port to add a temperature sensor.
I got cheapest Glowshift gauge, it works ok.
Have fun getting feed wire thru grommet behind brake booster.

https://www.google.com/search?q=glo...e=UTF-8&oe=UTF-8&hl=en-us&client=safari#fpr=r

 

[TJC]

I understand your quest. But I still think it’s a drainage thing. And could that be affected by temperature and or pressure also ? I’m guessing you would have to let it sit for a long time to let it all drain down. Maybe your test will establish that.

You may very well be correct. And if you are correct it will make it difficult to do a static fill accurately. I'll know in a couple of weeks as temps warm. If the level stabilizes it is drainage. If it fluctuates it will be pressure / temps.

 

[TJC]

The PPE pan has a port to add a temperature sensor.
I got cheapest Glowshift gauge, it works ok.
Have fun getting feed wire thru grommet behind brake booster.

https://www.google.com/search?q=glo...e=UTF-8&oe=UTF-8&hl=en-us&client=safari#fpr=r

I considered doing just that when I installed the PPE pan, but not sure where I'd put the gauge.

 

[got3fords]

If fluids can compress, then an engine wouldn't hydro lock when coolant leaks into a cylinder. Atmospheric pressure changes shouldn't make any difference in transmission fluid levels. Fluids do expand when heated, but I wasn't commenting on that.

I asked Gemini:

• In reality, all fluids are compressible.This means that their density can change when pressure is applied.
• However, the degree of compressibility varies significantly:
  • Gases:Gases are highly compressible. Their molecules are far apart, allowing them to be pushed closer together.
  • Liquids: Liquids are much less compressible. Their molecules are already relatively close together, making it difficult to significantly reduce their volume.
• In engineering and physics:
  • Often, liquids are treated as "incompressible" for simplicity, especially in situations where pressure changes are not extreme. The density change is so small that it can be considered negligible for many practical purposes.
  • Gases, especially at high speeds (approaching or exceeding the speed of sound), are definitely considered compressible. This is crucial in fields like aerodynamics.
    
• Key concept: Mach number:
  • The Mach number (the ratio of the fluid's velocity to the speed of sound) is a key factor in determining whether compressibility effects are significant.
  • Generally, flows with Mach numbers below about 0.3 are often treated as incompressible.

 

[Stevedbvik1]

You may very well be correct. And it you are correct it will make it difficult to do a static fill accurately. I'll know in a couple of weeks as temps warm. If the level stabilizes it is drainage. If it fluctuates it will be pressure / temps.

At some point it’s bound to be “totally “ drained. Just not sure how long that will take. Maybe never?

 

[RangerBill]

I asked Gemini:

• In reality, all fluids are compressible.This means that their density can change when pressure is applied.
• However, the degree of compressibility varies significantly:
  • Gases:Gases are highly compressible. Their molecules are far apart, allowing them to be pushed closer together.
  • Liquids: Liquids are much less compressible. Their molecules are already relatively close together, making it difficult to significantly reduce their volume.
• In engineering and physics:
  • Often, liquids are treated as "incompressible" for simplicity, especially in situations where pressure changes are not extreme. The density change is so small that it can be considered negligible for many practical purposes.
  • Gases, especially at high speeds (approaching or exceeding the speed of sound), are definitely considered compressible. This is crucial in fields like aerodynamics.
• Key concept: Mach number:
  • The Mach number (the ratio of the fluid's velocity to the speed of sound) is a key factor in determining whether compressibility effects are significant.
  • Generally, flows with Mach numbers below about 0.3 are often treated as incompressible.

The only time transmission fluid would be considered a gas is when it becomes aerated (air mixed in causing it to foam). For our discussion, this is not the case and atmospheric pressure changes would not affect the fluid level. Only temperature changes would come into play or drain-back from the torque converter or other spaces inside the transmission.

 

[got3fords]

The only time transmission fluid would be considered a gas is when it becomes aerated (air mixed in causing it to foam). For our discussion, this is not the case and atmospheric pressure changes would not affect the fluid level. Only temperature changes would come into play or drain-back from the torque converter or other spaces inside the transmission.

I was just sharing what Gemini spit out on the compressibility of fluid. Nothing more.

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