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best location for temperature sending unit

No, but it is in the pressure side. My GMTDScantech reads trans temp 20* cooler than my temp gauge. I don't know if one is off or the reading is from another point.
 
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Your gmtdscantech is reading sump temp via the temp sensor in the pan, the pressure port I'm pretty sure is right after the pump and should be close to where the fluid is the hottest. It wouldn't surprise me to see upwards of a 75 degree difference when you're really working it hard. I know my ALLISON runs 80-100 degrees hotter for the fluid coming right out of the pump going to the cooler than the fluid in the sump going into the pump.
 
I know the instructions for my gauge say to use the test port. Once I finally figured out where it was on one of my spares, it was easy to find in the truck.
 
I guess the choice comes down to do you take your temperature orally or rectally. Do you want to know the temp of the fluid leaving the tranny after it's been stressed and abused, or to you want to know the temp of the fluid sitting in the sump about to be drawn into the tranny and circulated around, or do you want to know both?
 
THEFERMANATOR said:
Your gmtdscantech is reading sump temp via the temp sensor in the pan, the pressure port I'm pretty sure is right after the pump and should be close to where the fluid is the hottest. It wouldn't surprise me to see upwards of a 75 degree difference when you're really working it hard. I know my ALLISON runs 80-100 degrees hotter for the fluid coming right out of the pump going to the cooler than the fluid in the sump going into the pump.
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Ferm, Is that a 1/8" NPT fitting on the side of the housing?

I can't recall who it was (over a decade ago), but someone told me that wasn't the best place to read the temperature from. I was told it would be better in the pan, but best on the output line. Since I didn't want to cut a line, I opted for the pan, since I have a drain plug there, anyhow, with the same size port (for the cost of a bung kit, it's silly to not install one). I'd love to have it in a place where I didn't need to mess with a wire every time the transmission is serviced, but wouldn't want to compromise, either. Are we talking about the same port?

It would also be nice to not have a wire hanging off the bottom of the pan. I've never had an issue, but it still isn't an ideal situation, in my opinion.
 
SnowDrift said:
Ferm, Is that a 1/8" NPT fitting on the side of the housing?

I can't recall who it was (over a decade ago), but someone told me that wasn't the best place to read the temperature from. I was told it would be better in the pan, but best on the output line. Since I didn't want to cut a line, I opted for the pan, since I have a drain plug there, anyhow, with the same size port (for the cost of a bung kit, it's silly to not install one). I'd love to have it in a place where I didn't need to mess with a wire every time the transmission is serviced, but wouldn't want to compromise, either. Are we talking about the same port?

It would also be nice to not have a wire hanging off the bottom of the pan. I've never had an issue, but it still isn't an ideal situation, in my opinion.
Click to expand...
It is a 1/8" NPT plug
THEFERMANATOR said:
Your gmtdscantech is reading sump temp via the temp sensor in the pan, the pressure port I'm pretty sure is right after the pump and should be close to where the fluid is the hottest. It wouldn't surprise me to see upwards of a 75 degree difference when you're really working it hard. I know my ALLISON runs 80-100 degrees hotter for the fluid coming right out of the pump going to the cooler than the fluid in the sump going into the pump.
Click to expand...
My GMTDScantech read 20* lower than the gauge while towing.
 
1/8" npt and your scantech is reading sump temp which will be colder than the test port where its reading coming out of the pump.
 
Depending on where the sensor is put, (test port, pan) and so on are there specific temps that the fluid should be at for those locations?
 
I like to read temp whenever its easily possible when it's at it's hottest point. Many times this is the fluid leaving the trans going to the cooler as it has just left the pump. For conventional atf, you want to keep temps under 235-240 as that is where it really starts to rapidly breakdown.
 
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