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Trans Temp Gauge: Pan vs. Inline probe

mfgguru

mfgguru

Makin' it better!
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Winkler, MB, Canada
I have been mulling this over and I believe that you get better readings from the transmission outlet cooling line than in the pan, but that may be wrong. Looking for your opinions as to which is a better indication of trans temp.
Secondly, what is the OD size of the cooling lines at the trans? I am thinking of using compression fittings and putting the probe in line.
 
3rd location option

Here's a 3rd location you might consider:

There's a test port in the chassis of the trans just above the linkages on the driver's side. (1/8" pipe IIRC) The same as the usual temp sensors.

I did it on mine. Easy to do. Just remove the plug and install the sensor.

Just my :2cents:
Cheers
 
snoman699 said:
Here's a 3rd location you might consider:

There's a test port in the chassis of the trans just above the linkages on the driver's side. (1/8" pipe IIRC) The same as the usual temp sensors.

I did it on mine. Easy to do. Just remove the plug and install the sensor.

Just my :2cents:
Cheers
Click to expand...

can you take a pic of this port snoman699? this is on the 4L80E trans right?
 
GmcLbz said:
I don't think it matters as long as you have a baseline to start with...
Click to expand...

I guess I just want the temp. to be taken at the point of hottest fluid. Then you know for sure that the oil going back in the return is a bit cooler. I guess the auxillary hole would be the easiest to do.
 
On my gassers 4L60E I just used that 1/8 in pipe port on the left side of the trans case, the sensor screws right into it and it gives a reading of the fluid thats flinging around inside the case along with the case temp too.
 
it is my understanding that port has high pressures, that aside, I tried that and an inline connection. the inline was way quicker to respond to fluctuations, therefore I believe more accurate.
 
I've had my tranny temp sensor plugged into that port for over 2 years now without any problems. I can't speak to an inline sensor but the response time on mine is good. I can watch the temp climb while pulling up one side of a mountain pass and drop as I cruise down the other. The actual time lapse (to when I see the gauge needle start to move) is about 15 to 30 seconds when climbing but longer when coming off the throttle and coasting downhill. However, when coming off the throttle after a climb and going into torque converter lock-up (where the rpm stay up) on a flat cruise, the tranny temp comes down noticeably faster than coasting. I asssume this is because the ATF is being circulated through the cooler a little quicker while not working the tranny too hard.
It was very easy to find the port/plug and install the sensor. I would think it is easier than working it into a cooler line. As I said though I don't know the advantages to the line install.
If you do decide on the port, you may want to give it a blast with a pressure washer beforehand. Just to get that layer of flatland mosquitos off you know...:rolleyes:
G'luck!
 
Oh, the mosquitoes are long gone. Now we have flippin' ice, snow and slush! Winter came early this year. SUCKS! Thanks for the input Fysh. I wish I was where you are now! At least you have something to look at!
 
I wasn't able to get a clear view of the port to take a picture. The park/neutral backup switch is in the way.

So, here's a drawing of the test port I was referring to.

The plug is 7/16".

Hope this helps.
Cheers.
 

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If you are concerned about high temp breakdown I would suggest a synthetic ATF. I'm running Red Line HighTemp Synthetic ATF and I really am satisfied with it. Smooth shifting at both high temps and low temps is a must for areas with the temp extremes we get, and I'm willing to bet your area is even more so. The stuff is stable at pretty well any temp we can throw at it. It is pricier but it doesn't have to be changed all that often. It's worth every cent.
 
Pan oil or test port temp. (close to the same) is a more important temp.. What you want to know is the temp that your oil spends 98% of its time at. Also you will have real numbers that everyone else can relate to, so you can identify problems. Example: you can ask on this forum if your trans temps are normal when your pulling a trailer or city driving. Converter output temps. will show high temps and will swing radically but so what it will be cooled in seconds and no one can help you with what temps you should be seeing. Here is a chart for trans temps but it won't apply if you put the probe in the trans output line, http://www.txchange.com/heatchrt.htm Trans. Shops likely wouldn't even be able to help to tell you what the output temp should be.
 
I sort of monitor 2 places pan temp, my PML pan was bossed for tapping of a sensor, that is displayed on my gauge pod, and my Deraile cooler/fan temp switch turns on the fan >180F return oil temp, and is place where that vendor recommends it be installed, the fan/cooler I mounted under the bed keeps pan temp <200F even when hauling 18K loads on 100+ day, normal empty hauling I'm running 150-180 depending on how hard I'm pushing it
 
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