transmission temps

[puller]

I had a new transmission installed in my truck and when taking it for a test drive the tech had the computer hooked up to the factory computer port as we drove around, I noticed the temp readings he was giving me were different than the readings I was getting from my gauges (I have a inline sensor and isspro gauges). His readings 155 degrees my readings 130 degrees.



My question is does anyone know where the factory gets the temp readings from that are relayed to the factory computer?



Puller

 

[cerberusiam]

Factory sensor is on the VB.

 

[puller]

What is a VB when you got one?



Puller

 

[JDiepstra]

Are you asking what is a Valve Body?

 

[cerberusiam]

What is a VB when you got one?



Puller

Sorry, :-laf VB is easier to type than valve body. Its in the pan area of the transmission and reading fluid temp after it returns from the cooler and is used as trans lube and cooling.

 

[puller]

Thanks for clearing that up. Now I have to question if I did the right thing in listening to everyone that said the sensor should be in the output line going to the coolers, maybe it should be in the pan. I do have a mag-hytec double deep pan but that should not make a difference.





Puller

 

[cerberusiam]

Thanks for clearing that up. Now I have to question if I did the right thing in listening to everyone that said the sensor should be in the output line going to the coolers, maybe it should be in the pan. I do have a mag-hytec double deep pan but that should not make a difference.





Puller

No, the output line is the correct place. You are seeing the difference between what the ECU is reading (digital) and the analog gauge.



Placement of the probe in the output line can make a difference also. If it is not far enough into the flow it will read a little low, or it could be correct and the pan sensor is reading a little high. Calibration between the 2 is probably not going to be the same.



The reading from both gauages is well within the operating range. The trans will generally stay within 20 degrees of engine temp depending on how you drive it.



Where you will see the difference is under a load, TC unlocked, and lower rpms. That is better monitored on the output line to see if you need to manual downshift to keep from cooking the fluid in the TC. The pan sensor will slower to react as it is reading fluid temp after it has been thru the cooler.

 

[puller]

cerberusiam,



That is what I was always told that the best place is in the output line. I know that the sensor is in the fluid stream because I went the extra step and went to a place that sells fittings for hydraulic applications and we tested it there. It was tested for flow as well as temps.

I guess I needed to hear it one more time to reassure myself that I did the right thing.



Thanks



Puller

 

[cerberusiam]

cerberusiam,



That is what I was always told that the best place is in the output line. I know that the sensor is in the fluid stream because I went the extra step and went to a place that sells fittings for hydraulic applications and we tested it there. It was tested for flow as well as temps.

I guess I needed to hear it one more time to reassure myself that I did the right thing.



Thanks



Puller

If you tested the analog gauge install for temps I would definitely rely on it.



I have serious concerns about the accuracy of the factory trans temp sensor. They seem to be really inconsistent with their readings. The performance boxes that tap then always seem to be reading higher than an analog gauge in the same spot. Couple that with the fact they are the cheapest electrtonics possible I put much more faith in an analog gauge.