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4l80e fluid flow

cuervo

cuervo

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So looking at this scan I made out of the manual it looks like the pressure test port(green circle) comes straight off of the pump.

I'm putting in a temp gauge and I don't want to weld a bung on the pan or put in a new pan either. I've also read about which line to use, outbound tells the hottest temp, inbound tells you what the tranny will be using, use the pan its what's going to be used.

It seems the pressure test port is the accual fluid temp that is being used and I'm thinking this is the best bet for keeping an eye on it.


transflow.jpg
 
I used the high pressure port on my 700R4. It probably wasn't the best. The fluid actually dead heads in that area. You will also pick up case temp.
You will still get readings though. I used it for a baseline. I knew it was always hotter than it really was.

Why don't you put a T in your cooler lines? Either one, in or out. There is many opinions out there on which is best.
I think it doesn't matter. It should be used as a guide. When you are just out cruisnig you will see what your "Norm" is. When it starts to climb above that you know you need to watch it and if it gets to high, stop and do something about it.

my .02
 
My opinion says to read the line out to the cooler, this will tell you how hard your trans is working, and the highest working temp the trans has incurred. Heat is what kills a trans, so if you can read your output, you'll know what temp it has been subjected to.
 
The best place is in the pan, this is because you want to read the temp on fluid that isn't rushing past a sensor (which has a cooling effect) and it is the true temp since you aren't reading fluid temp after it's already been cooled (return line) or after it has already been worked hard (pressure line) and heated.
 
Where do the stock equipped trucks get there temp from?
 
Most don't that I know of, but if you look in that diagram you can clearly see the temp sensor.

And, I'm going to go with the pressure point at this point.

If I had to pick a line it would be there return line. I figure if the fluid temp is getting so hot that it can not be cooled then you KNOW you have a problem
 
I think the 99 and up 2500's have them with the 4L80E....at least 2 of them I've seen have them.
 
All electronically controlled gm transmissions have temp sensors, for pcm or tcm reference. They are located in the pan.
 
rd2116 said:
All electronically controlled gm transmissions have temp sensors, for pcm or tcm reference. They are located in the pan.
Click to expand...

Where ever that sensor is located it is on the same fluid line as the pressure test line.
 
The sensor in the 4l80e is acually attatched to the internal wiring harness in the pan. I have no idea why that schematic shows it as being in line with pressurized fluid because its not.
 
rd2116 said:
The sensor in the 4l80e is acually attatched to the internal wiring harness in the pan. I have no idea why that schematic shows it as being in line with pressurized fluid because its not.
Click to expand...

If that is the case, I'm wondering if I could just tap the wire coming out of the harness and use the internal sensor? That would be pretty awesome it's possible.

I'll dig through the wiring diagram book I have.
 
It should be possible, its a 2 wire sensor with a 5 volt reference and a low reference so it depends on what kind of gauge you have, hopefully that helps. Good luck with it.
 
rd2116 said:
It should be possible, its a 2 wire sensor with a 5 volt reference and a low reference so it depends on what kind of gauge you have, hopefully that helps. Good luck with it.
Click to expand...

I found this information about the temp sensor as well.

Code: 
 I couldnt buy just the temp sensor, it's made into the harness

Any idea if this is the case?
 
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