Can I install this temp sensor in Ford E40D test port?

That test port is where the temp probe belongs. It will give you about the same temperature as oil in the oil pan. It is from the oil pan that the tranny draws its oil supply. That is the temperature the tranny will live-or-die by. After the oil goes through the torque converter and the rest of the transmission, it naturally heats up, but once it goes through the coolers, much of the heat is dissipated and the oil is cool enough for reuse from the oil pan, unless there is an overheating problem which the oil pan temperature will show. Monitoring that temperature is what counts the most IMHO.

I had read lots of posts on the internet that debated where to put the transmission temperature sensor. Lots of debate and lots of incorrect information. Ran across more than one post that suggested putting it on the fluid return line, which is going to give you the cooled-off fluid temp as it comes back from the fluid radiator, which is useless! Likewise the pan is where the return fluid collects before being sucked up back into the transmission to be heated up again, so it also is not a very good place to find the max temp of your transmission.

Finally had input from a fellow who claimed to be a Ford transmission engineer. He said the test port was fine.

The test port is a dead-end port, so you won't have fluid passing by it. However, the aluminum transmission conducts heat well, so the test port will accurately reflect the overall temperature of the transmission. But, even being a dead-end port, as you can easily see when starting the engine from cold it does not take long for the sensor to start noticing temperature increases and come up to operating temperature. Likewise, downshifting on hills quickly shows up on the test port sensor also.

A port in the outgoing fluid line will give you the transmission fluid maximum temperature, and one would expect it to more rapidly track changes in fluid temperature than the one in the test port, which would lag behind. But the test port sensor does not lag too badly, as I noted above.

I went with the test port because it was super-easy to install. Remove the port plug, screw in the sensor, and you're done. Tapping into the fluid outlet port requires a T fitting and making sure you don't cause a restriction.

Steve

topic

When I had the E4OD I used to argue against using the test port for a gauge. Before selling, I had two input to my gauge, one from the hot line and one from the test port. Comparing the two showed the test port to be a bit more accurate IIRC. Here is a post about it and a picture I took when I had my E4OD rebuilt.

Sorry, double.

Test the depth of the test port with a nail. Gently.

maillemaker wrote:
By the way, it looks like replacement GlowShift sensors are only about $20:

https://www.amazon.com/GlowShift-Replacement-Temperature-Sensor-Sending/dp/B078XJTQ3R

Steve

About the time you sent this I was online with their tech support by chat message and they have suggested some tests of resistance.

I will be doing this soon to zero in on the problem.

Thanks!

By the way, it looks like replacement GlowShift sensors are only about $20:

https://www.amazon.com/GlowShift-Replacement-Temperature-Sensor-Sending/dp/B078XJTQ3R

Steve

This is the kit I used on both our current and previous coaches, and yes, the sender was installed in the test port on both. The previous coach has had the B&M gauge in service for about 10 years and it still works fine according to the current owner. The gauge in our current coach is only 5 years old, but it's still working fine as well.

B&M 80212 Transmission Temperature Gauge Kit

Well, that's disappointing.

So far, my GlowShift has worked well for me so far. I'm not even going to bother trying to plumb a sensor into the output line. The test port seems to be giving good, stable temperature readings around 170F-180F.

Steve

Can anyone recommend a digital temperature sensor that has lasted for several years?

I have a GlowShift that stopped working shortly after the warranty expired.