I'm trying to figure out where you get the most reliable measurement of tranny fluid temps. My 2001 Caravan's dipstick states that the fluid should be between the cold marks when the fluid is cold - 80 degrees F, and between the Hot marks when the temp is 180 degrees F. Just wondering where I should measure the temps, on the dipstick or at the tranny pan. The temperature of the tranny pan is far different than the temperature of the fluid on the dipstick, the tranny pan is always much higher. I can run the car in heavy city driving in 90 degree weather for an hour or more, and the fluid will be luke warm on the dipstick, measuring 80 degrees or so, but when I measure the temperature of the tranny fluid pan it will be over 160 degrees. (using an infrared heat reader gun). I can't see the temp of the dipstick ever being anywhere close to 180 degrees , but I could see it at the tranny pan. So what is the more reliable measure of tranny fluid temps ?. any advice would be helpful. thanks.
Measuring Tranny Fluid Temperature....
- Thread starter Idrinkmotoroil
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Definitely take the readings at the tranny pan. The thin film of oil on the dipstick will cool almost instantly when you pull it out to take a reading.
Having nearly burned my fingers many times on automatic transmission dipsticks I can assure you that this is not the case. In fact, your owner's manual may give you an idea of how to tell how warm the fluid is on the dipstick. Anyway, I'd use the fluid on the stick.
Is there a place where you could run the car for an hour at highway speeds in that weather? Pull the dipstick after that and I think you'll find that the fluid on it is very, very warm. If not, perhaps thermostatic control of the cooler is in order...
The trans pan. You can do that via the dipstick because the dipstick tip sits in the fluid that's in the trans pan. Or you can get a vacuum pump and pull some trans fluid out of the pan and do it that way.
Having nearly burned my fingers many times on automatic transmission dipsticks I can assure you that this is not the case
really? I remember last summer doing 80mph in 95 degree heat and stopping at a gas station and decided to check the tranny fluid ...stone cold! couldn't belive it...oil dip stick so hot had to pull it with a rag !
really? I remember last summer doing 80mph in 95 degree heat and stopping at a gas station and decided to check the tranny fluid ...stone cold! couldn't belive it...oil dip stick so hot had to pull it with a rag !
Doesn't this require VAG-COM? If the tranny fluid temp. can truly be measured using an OBDII scanner, please tell me how.
The trans fluid in the pan is the most accurate place to take a "operating temp" sampling of the fluid. How you get to it is up to you. A long tube hooked up to a vacuum pump snaked down the dipstick tube is probably the easiest way to get a sample if you don't have a drain plug on your trans pan. I can absolutely, positively guarantee the fluid will not be cold...try at least 120F and no doubt higher than that if you've been driving it around for awhile.
Once the TC locks up on the highway, the transmission will cool down. Plus, there's a ton of airflow over the transmission body, usually aluminum, that will cool it down when driving fast.
Dipstick temp is the same as the pan. Plus, once the dipstick is wet with ATF(by the level), the temp of the dipstick is irrelevant. Its the average total ATF temp that causes the fluid level to change, not the dipstick temp! Measure temp at the pan.
For those with e-fans and ATF coolers built into the engine's radiator, the fan cycling becomes a temp probe. How??? Drive your car until tranny is hot, let car idle for 5-10 minutes in park and count radiator e-fan cycles, after 3-4 fan cycles, your unloaded ATF temp will match the coolant temp which should be just right for checking the level.
Dipstick temp is the same as the pan. Plus, once the dipstick is wet with ATF(by the level), the temp of the dipstick is irrelevant. Its the average total ATF temp that causes the fluid level to change, not the dipstick temp! Measure temp at the pan.
For those with e-fans and ATF coolers built into the engine's radiator, the fan cycling becomes a temp probe. How??? Drive your car until tranny is hot, let car idle for 5-10 minutes in park and count radiator e-fan cycles, after 3-4 fan cycles, your unloaded ATF temp will match the coolant temp which should be just right for checking the level.
I have found checking tranny fluid to be difficult and confusing regardless of vehicle owned. A couple years ago I decided that using the same method (per vehicle) to check was more important than following the manufacturer's directions precisely to the letter. For example, my Nissans give general directions for checking the fluid cold and hot based on things like "normal operating" temp and a driving at least 5 miles. Not too exact!
Sooo...I checked the hot and cold readings the very same way on 4 consecutive days. Since the manual said to check cold readings with the engine at normal operating temperature BEFORE the car is driven, I did that in the morning when I knew the engine would be cold before I turned it on. I recorded the time I allowed the engine to reach normal operating temp using the dash temp guage and then repeated the process the same way 3 more mornings. Not too surprisingly, I got the exact same "cold" dipstick reading each day. For hot readings I drove the car the same route, the same distance, the same length of time 4 days in a row, and...you guessed it, recorded 4 identical hot readings on the dip stick.
This was with the factory AFT fill by the way. By doing it 4 times I satisfied myself that I was getting a reliable mark on the dip stick, and I quit worrying if I did it the correct way Nissan meant it to be done. For as long as I own those cars I will always know what the correct reading on that dipstick should be when changing or checking the fluid levels.
Sooo...I checked the hot and cold readings the very same way on 4 consecutive days. Since the manual said to check cold readings with the engine at normal operating temperature BEFORE the car is driven, I did that in the morning when I knew the engine would be cold before I turned it on. I recorded the time I allowed the engine to reach normal operating temp using the dash temp guage and then repeated the process the same way 3 more mornings. Not too surprisingly, I got the exact same "cold" dipstick reading each day. For hot readings I drove the car the same route, the same distance, the same length of time 4 days in a row, and...you guessed it, recorded 4 identical hot readings on the dip stick.
This was with the factory AFT fill by the way. By doing it 4 times I satisfied myself that I was getting a reliable mark on the dip stick, and I quit worrying if I did it the correct way Nissan meant it to be done. For as long as I own those cars I will always know what the correct reading on that dipstick should be when changing or checking the fluid levels.
Generic scanners, at least the cheapo ones, definitely do not read ATF temperature.
The tranmission isn't doing alot at 80 mph because the TC is locked up and the trans has lot of iar flowing over it
I hardwire the e-fan on every car I own during the summer to keep the transmission temperature low. In city traffic with the fan cycling on/off the transmission can only cool down to 200F (the transmission temperature is probably higher than that). Old transmissions lasted a long time but they never ran as hot as transmissions today with electric cooling fans behind the radiator.
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