i have two isppro tranny gauges. one installed in the hot line and the other installed in the tranny port.temps have been in the 70's here the last couple of days. i have noticed if if i am in stop and go traffic or driving at relatively low speeds (30-45mph) the fluid readings on the "cool side" can be less than 15 degrees difference in temperature than the temp reading on the hotside. hotside-160 degrees, cool side 145 degrees. cruising down the interstate temp difference can be as much as 30 degrees. i would think the temp difference should constantly be greater than only 15 degrees?? thoughts? thanks.

 

I originally had my isspro in the test port. Later moved it to the hot line. If you want to see a huge difference tow something and compare

 

what temps are you seeing in the hotline driving empty?? i would think i should see a bigger difference in temps!

 

You need airflow to make the cooler effective. 15* in town sounds about right. I've seen up to 45* on motorhomes with way oversized coolers.

I would think the hotter the hot side is, the larger the spread between the two.

 

Well, for example my overhead read 83F today. Stop and go heavy traffic, city driving with no load my hotline read 185F. In the past the test port reading was slow to react and only went to 190F with a 7500# trailer. Now I find the hot line moves like the pyro with a load and warm weather. Does this answer your question. Point is load the tranny and you'll notice a big difference between the stagnant test case reading port reading and the hotline. I find that running the air really helps lower the tranny temps.

 

You are reading heat soaked stagnant fluid temps in the the test port. Fluid does not circulate at the test port and it will always read higher than return fluid temp. The temp will always read around 130-150 due to the fluid-to-fluid cooler maintaining a constant temp using the coolant. You need to run the truck hard wth a load and no lockup to see the diffference between the 2 places.

FYI, if you tapped the test port on the back side of the trans with the probe, you are running a big risk of destoying your transmission. Get it out now if you can.

 

thanks guys- your answer's make sense. the probe is installed in the port on the side of the tranny.

 

FYI, if you tapped the test port on the back side of the trans with the probe, you are running a big risk of destoying your transmission. Get it out now if you can. [/QUOTE]

Ok-- now you have me worried. This is where my temp gauge is mounted.

Why the danger? What could happen?

 

Its a test port for accumulator pressure. There is a piston inside the bore the port is on and it can move out far enough to contact the end of the probe. Worst case it will bend the probe up enough you cannot remove it, break the piston causing damage to both the case by gouging the bore and the rest of the trans by droppping pressures.

It will depend on the probe size and the piston design if this will happen sooner or later, but, it is inevitable you will have some type of contact over time. Just not a good place for the probe for those reasons and the fatc it is not reading true max fluid temps.

 

Ok-- Thank you for clearing that up! It explains a problem I had in the past and the local dealer that installed my gauges put it there and had to replace the sensor after it did exactly what you describe!
I think they should have known better. Oh well-- so then, can you please describe exactly where the sensor is supposed to go so I can relocate it?

 

I use the hot line for mine. I bought the cooler line that is already set up for it from dieselmanor.com

 

And they put it BACK there again????

The best most accurate place for the temp probe is the cooler output line of the transmission, front cooler line drivers side of trans. Either cut the rubber vibration hose and insert a fitting or get the line with the fitting built in.

 

Yes they did! and the owner of the shop was vocal at the mechanic that "put it in there". He thought the guy put it in wrong or damaged it himself. He had no idea of what you described. And certainly I was ignorant!

Thanks much for the info

 

Curious.... did they use the "sender extender" that is offered with the gauge kit?

 

One thing to remember is that the fluid coming out of the transmission is hot. We know that. That is why it goes through a cooler. The return line has cooler fluid because it has been through the cooler, but that is not what the tranny is taking back in. The Pan temperature is ideally the one you want to know. It has the actual temperature of the fluid being introduced back into the transmission. If it is too hot it isnt lubricating the way we want it to. If someone doesnt want to drill and braise in a fitting into the pan you could go with a deep sump pan that is already drilled and setup for a temp probe, plus you are gaining a couple of quarts of fluid to help keep it cooler. Oh yah by the way we sell deep sump pans too.