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

[5thranger]

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.

Starting to get anxiety attack from this conversation.

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[IdahoRanger]

Starting to get anxiety attack from this conversation.

I'm just getting gas. ?

 

[Grumpaw]

I'm just getting gas. ?

 

[Frenchy]

Many modern transmissions are using fluid that can easily change the level with little temperature change. It's certainly interesting to say the least. At the same time it is a pain. My suggestion is to make sure the fluid level is correct at operating temperature and it might be better to be just a little low(like in the middle of the hot section of the dipstick).

 

[TJC]

Atmospheric Pressure and Temps dropped overnight, and so did the fluid level. Ever Onward!

Correlation does not equal Causation... Skid marks do not cause accidents!

Still a ways to go to really validate the possibility of finding a simpler way of accurately checking the transmission fluid level. I think by mid summer when the heat is up I will have a solid feel for the reality of what is going on.

Of course I could simply heat up a quart of transmission fluid and and measure the expansion rate, then apply it to whatever the transmission holds (12quarts?). But I still don't know how much fluid it takes to raise the level to a given point on the dip stick.

There are lots of ways to skin a cat...

 

[Big Blue]

Many modern transmissions are using fluid that can easily change the level with little temperature change. It's certainly interesting to say the least. At the same time it is a pain. My suggestion is to make sure the fluid level is correct at operating temperature and it might be better to be just a little low(like in the middle of the hot section of the dipstick).

I agree. A chart to show level variations using the normal checking procedure at various temps at or near the recommended operating temperature. Such as 180, 190, 200 and 210 degrees F, would be more useful. I find it difficult to get and keep mine up in the recommended range for checking. I find it hard to get mine over 190 unless I'm towing my TT.

 

[brroberts]

I agree. A chart to show level variations using the normal checking procedure at various temps at or near the recommended operating temperature. Such as 180, 190, 200 and 210 degrees F, would be more useful. I find it difficult to get and keep mine up in the recommended range for checking. I find it hard to get mine over 190 unless I'm towing my TT.

Even when towing I am often below 190. It’s rare I see 210 to check it. I’d have to have 210 and a level place for truck and trailer just to do a rare factory spec trans level check. It’s never happened. I did see 225 once towing up and down long winding 17% grades. Let it cool at the top before heading down, but it was not level enough to check it there which was before the Fitzstick and PPE pan.

 

[Stevedbvik1]

I agree. A chart to show level variations using the normal checking procedure at various temps at or near the recommended operating temperature. Such as 180, 190, 200 and 210 degrees F, would be more useful. I find it difficult to get and keep mine up in the recommended range for checking. I find it hard to get mine over 190 unless I'm towing my TT.

I can make it do 205-215 pretty much on demand. About a 15 minute drive at highway speeds in 6th gear ( 3500-4000 rpm). I imagine you could do it at lower speeds with picking a gear that keeps the rpm up for an extended period. Of course when it’s-10F it’s probably a different story but who wants to check transmission fluid levels then?

 

[Big Blue]

I can make it do 205-215 pretty much on demand. About a 15 minute drive at highway speeds in 6th gear ( 3500-4000 rpm). I imagine you could do it at lower speeds with picking a gear that keeps the rpm up for an extended period. Of course when it’s-10F it’s probably a different story but who wants to check transmission fluid levels then?

I haven't tried that yet, but may have to. The only time if seen mine get over 200 was pulling my TT across Arizona at 70mph in 8th gear. Only time it any where near 220 was in the mountains north of Phoenix.

 

[got3fords]

Starting to get anxiety attack from this conversation.

View attachment 229237

Even when towing I am often below 190. It’s rare I see 210 to check it. I’d have to have 210 and a level place for truck and trailer just to do a rare factory spec trans level check. It’s never happened. I did see 225 once towing up and down long winding 17% grades. Let it cool at the top before heading down, but it was not level enough to check it there which was before the Fitzstick and PPE pan.

This is why I don't have any faith in proper fluid level checks, even with the dealer. Do you think they actually get the fluid temp up to 210'sh? I seriously doubt it. When I took it back after they overfilled my tranny the receipt stated something to the effect that they ran the truck for about an hour and checked the fluid. I seriously doubt it was up to around to 210, but at least the Fitzstick allowed them to get it close enough that I haven't had the overfill issues.
And damn, new fluid is so clear it is really hard to read on the stick.

 

[Swede726]

I can make it do 205-215 pretty much on demand. About a 15 minute drive at highway speeds in 6th gear ( 3500-4000 rpm). I imagine you could do it at lower speeds with picking a gear that keeps the rpm up for an extended period. Of course when it’s-10F it’s probably a different story but who wants to check transmission fluid levels then?

Yeah. It's so easy to run the ranger hot when you can lockout gears. I just recently installed the MBS diptstick and found my level at exactly 4.5 hot and it really doesn't vary much from that when warmed up. It's always around 3-3.5 when cold. I'm at 35k and plan on doing the fluid soon.

 

[Dereku]

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.

They do compress, ever so slightly. Not enough to prevent engine failure. Thermal expansion and contraction is much more noticeable. Humidity and dew point play a larger role than barometric pressure. As humidity allows better thermal transfer.

 

[Swede726]

If anyone wants a super cheap way to monitor temps I just got a cheap ob2 dongle and use a free ap.

I bought a $30 Veepeak OBD 2 Bluetooth and the free ap from carscanner.info.

Can see my transmission temperature live and even chart it. I think most would be surprised how long it takes to warm it up. It seems to run around 170-180 mostly here in New England in where it's been cold. Will have to see what temps it runs as it warms up. It also displays a ton of other data.

 

[got3fords]

If anyone wants a super cheap way to monitor temps I just got a cheap ob2 dongle and use a free ap.

I bought a $30 Veepeak OBD 2 Bluetooth and the free ap from carscanner.info.

Can see my transmission temperature live and even chart it. I think most would be surprised how long it takes to warm it up. It seems to run around 170-180 mostly here in New England in where it's been cold. Will have to see what temps it runs as it warms up. It also displays a ton of other data.

Boy, that PCM odometer is HOT!

 

[Stevedbvik1]

Boy, that PCM odometer is HOT!

I think you should check with @AzScorpion to see if 303 makes a pcm odometer coolant enhancer

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