I have my trans temp sender in the drivers side port of the transmission like most people do.

My question is
What's more important. Temp out of transmission (so you know operating temp) or pan fluid temp (that fluid will cool trans) or return fluid temp (from cooler)

I'm assuming operating temp is most critical but is that the temp we are getting from the service port or is that really case temp or mostly fluid temp because the sender really doesn't protrude into the flow of the fluid really.

 

I have my sensor in the test port and it's pretty close to what AE says the trans temp is. I think the test port was about 4-7 degrees cooler compared to what AE said.

Sensor in the pan was way off. Took forever to register and once it did it never was close to what AE said. I have always thought that the fluid temp in the pan is about the same as the fluid temp returning from the cooler. I purchased a F450 a couple of weeks ago and the previous owner has a sensor in the test port and another one in the pan. There is a switch on the dash that flips back and forth between the two, it's labeled "Trans Body Temp" and Trans Cooler Temp". I am not sure if those labels are exactly accurate but I suppose it's gets the point across well enough.

 

When Brian (BTS) over hauled my tranny, I asked him about where to put the temp sender and he said the drivers side port is the place and pointed out right where to put. Good enough for me.

 

Use the provided port, it's the most common. Otherwise your trans temps will not be comparable apples-to-apples with everyone else, if you know what I mean.

 

If you only have one temperature reading, you want to know the temp at which the tranny is actually performing. The temps pre- and post-cooler are only useful if you're trying to evaluate the effectiveness of your cooler. As long as your actual operating temp is good, then the other pieces of information are only academic.

Regarding the small difference between the housing port temperature and the AE value, that is perfectly normal. Since the housing is exposed to air flow at lower tempeartures (than within the tranny), there will be a very small difference due to the cooling effect of the air flwo around the tranny. No big deal. if the port is at a level which is below the fluid level in teh sump, it should not really be any more than about 2-3 degrees difference, and I say that based on what I've seen in field temperature measurements on hundreds of manufacturing pipelines which run anywhere from 140°F to over 500°F. On the other hand, if your housing port is above the liquid level in your tranny sump, then you will actually get a larger difference because the air inside the tranny will not transfer temperature as effectively as will teh tranny fluid, and the difference could easily be in the 4-7 degree range.

If you know all of this going into the situation, then you simply keep a mental note active in your mind which tells you that the temperature INSIDE the tranny is slightly hotter than what your gauge reveals.