I would run the temp sensor closer to the transmission. Thats the input line into the head exchanger. I ran one of those temp sensors, its not quite as good as a pan measurement. My inline showed erratic temperature measurements and was prone to failure.

I currently run an autometer trans temperature in my magtec trans pan. I also run a dual electric fans trans cooler. My max trans temp is 180 deg's when I tow. At 180, the fans are set to maximum. The fans kick in at 140 deg's on the low setting.

 

DTT Transmission

One of the favourite locations by people is the front servo on the passenger side of the transmission. The problem with that is there is no oil in that port in first gear, 2nd gear, or reverse so what are you measuring?
If you do have a transmission temp sensor in that port, take it out, not only is it not monitoring your oil it is probably causing damage to the transmission as the probe is most likely making contact with the servo spring.

Middle port passenger side better known as accumulator port is another, while this port does measure transmission temp in first, second, drive and od, it is measuring stagnant oil. It other words oil fills up and stays there. There is no oil present in the accumulator while you are in the reverse position. So it is useless to measure from this location also.

Another favourite place is in the reverse port on the passenger side. This port only has oil in the reverse and manual low positions. This means no oil in the in the drive position. I have had guys phone me arguing with me that they are seeing temps of 200 degrees while driving down the road in stop and go traffic when measuring from this port. My comment to that is congratulations we now know the temps of your tranny case, we can only guess at this point what your tranny temps are.

As far as I am concerned, there is only one location to accurately measure your tranny temps from. That is your transmission cooler outline. I have seen temps get as high as 300 degrees coming out of that line. That line sees every 20 seconds 1 quart of oil pumped through it at 1100 rpms. 3.8 gallons at 2100 rpms every minute, in 3 minutes you have pumped out basically 12 gallons of oil. So lets say you see temps of 300 degrees from this line and you have pumped it through your tranny At this point in time you can change the oil in your tranny or you can wait a little longer and change your tranny , rest assured you will be doing one or the other. I don’t make any extra money selling you guys the Chrysler lines, I give you the number we use, 5011244AA. The 1995 and earlier trucks it is a little more difficult to hook up the tranny temp gauge, but the 96 and later trucks you guys only have one choice, use the Chrysler line if you tow and want an accurate reading. To me, a gauge is there to monitor temps and indicate how often to change the oil. Since this is about a 3rd gen truck we purchase the line from one of our dealers Mass Diesel 1-508-660-7093, known as Scott to some of you as there is nothing from Chrysler and Scott did if first.

 

Chrysler p/n 5011244AA, output line with sensor port crosses over at Napa for almost exactly half the price as the dealer - $47.

 

Absolutely the ONLY accurate way to measure the temp. Using the test port is an absolute joke!

 

Cool, I did not know NAPA had one, I've been using a Swaglok fitting, they have a two piece ferrule, never seen one leak once it was put together. They are about 55 bucks, but are a very high quality fitting made of SS. I order the 1/2 tube X 1/2 NPT X 1/2 tube and bush the pipe threads on the "T" down to 1/4 or 1/8 NPT depending on the senor that you get with the gauge.