I added a transmission temperature gauge to my truck last night and, after much research (on this forum) about where to put the trans temp gauge sender unit, I decided to take the easy way out and put it in the test port of my 2001's 4R70W. Unfortunately it doesn't seem to be working. I drove around last night for about 10 miles of city traffic and the gauge never budged over 100. I made several stops and could feel that the transmission pan was well above 150 but the gauge never showed it. I'm confident the wiring of the gauge is correct.

My question is: how long does it take to get the trans up to normal operating temperature and how slow does the test-port mounted sender respond to temperature changes? Thanks!

 

I mounted mine in the return line from my cooler.

 

THe test port is for pressure test and the fluid does not circulate through it . if you want an accurate read put the sender in the pan this will also give you the advantage of a drain plug a 2nd option would one of the cooler lines but the read will be different depending on which line you choose. [It will read less on the retun line].

 

Do not point it in the pan. The temp in the pan is inaccurate to exactly what the fluid is doing. It is best to have it in the return line. The pan will get heat soaked. The output line will spike well over too when the converter clutch is slipping.

 

Not to start an argument but the oil in the pan is the oil that is being fed into the trans and where the oil from the cooler is returned. so the most acurate oil temp read is taken from where the bulk of the oil feeding the trans is at. And as to the converter clutch the only time it slips is just for a split second as it locks up. the purpose of the clutch is to prevent tourque converter slip the heat build up in the converter is cauesed by coverter fluid coupling slip not clutch slip and is normal and yes the oil out to the cooler will be hotter than the oil return thats the purpose of the cooler but the overall trans temp is best measured in the sump that is where the factery and most after market supplyers take there read

 

So after a weekend of driving around, I found that putting the sensor/sender unit in the test-port DOES work. It gives an accurate temperature but the downside is that it takes a very long time to respond to temperature changes. For long trips and highway miles the location would give me an indication of the temp but the slow reaction time is less than desirable. I'll be moving the sensor to the line going to the cooler instead just as soon as I can find one of those fittings...