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The ‘Right’ Way To Install a Transmission Cooler

sgtsandman

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Wrong brand of vehicle but the concept is the same. Note the part he mentions about the warranty at the beginning.

One thing I was taught for systems that don't have the warranty claim is to install the line from the transmission to the auxiliary cooler input and then the auxiliary cooler output hose goes to the factory cooler input in the radiator. Then the hose from the factory output goes to the transmission.

Reason being is that the newer, computer controlled transmission are temperature sensitive. If the transmission fluid is too cool, it could cause the computer to think the vehicle is in warm up mode and enrich the fuel to the engine. This can cause poor fuel mileage as well as issues with DTC codes and emissions system failures. Running the cooled transmission fluid through the factory cooler will allow the fluid to warm back up and prevent this. Newer automatic transmissions have a temperature sensor in them, thus the potential issue.

Another option is to install a thermostat in the transmission cooling system that will prevent too cool of a fluid going through the transmission but you may need to install a bypass to prevent starvation issues to the transmission, adding to the complexity and cost. It depends on the transmission and how it is setup.

 


RonD

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+1 ^^^

Transmissions, like engines, work best when fluid temp is between 175 and 195degF(coolant temp for engines)

Fully warmed up radiator should be about 170-180deg at the bottom or side where the trans cooler is located, so it will cool trans fluid thats above 180degF and keep fluid warmer that's below 170degF

So added trans cooler would be best on the OUT of trans line, and then to rad cooler, so rad cooler can warm it up or cool it more which ever is needed
 

DILLARD000

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Honestly with this 5r55e, I have not noticed any significant difference in shifting,
from when Tranny is first running cold on winter mornings & Tranny Temp is <100f,
to when its running fully warm on a hot summer afternoon & Tranny Temp is >170f.
May be because I normally drive like a 70yo ChurchLady;
only really push this engine+tranny hard when running up 5%+ mountain grades on
highways getting round "FlatLanders" who don't comprehend the concept of downshifting.
 

bobbywalter

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My credo
it is easier to fix and understand than "her"
Many of The new transmissions internally bypass and only send fluid out when it wants it cooled.

3 mpg was the difference between 130 degree or lower temp fluid in my aod with a mild 302... And 180 degree fluid.

I built a manual bypass manifold for it because I only had a 17 gal tank for a long time. My cooler was UNDER THE BED... Even wrapped in a blanket getting over 140 deg was tough in winter.
 

RonD

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Most of the heat in an automatic comes from the torque converter
So stopping in gear generates heat or slow driving so torque converter can't lock
And of course pulling a load does as well until torque converter can lock

And if trans gets old or low pressure then slipping clutches and bands add to that heat
 

sgtsandman

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4.0 SOHC
Transmission
Manual
2WD / 4WD
4WD
Total Lift
Pre-2008 lift
Tire Size
31X10.5R15
Honestly with this 5r55e, I have not noticed any significant difference in shifting,
from when Tranny is first running cold on winter mornings & Tranny Temp is <100f,
to when its running fully warm on a hot summer afternoon & Tranny Temp is >170f.
May be because I normally drive like a 70yo ChurchLady;
only really push this engine+tranny hard when running up 5%+ mountain grades on
highways getting round "FlatLanders" who don't comprehend the concept of downshifting.
It depends on the design. I think the 5r55e is a bit of an older design that the computer doesn't worry about the transmission temp so much. I first learned about the transmission fluid temp being an issue when I was into the Honda SUV thing. People were having mpg problems, emissions problems an so on when they installed a transmission cooler the "wrong way" and the transmission couldn't get warm enough.

I've been paying attention to the transmission temperatures on the 2019 when hauling and towing. If it looks like it's going to be a problem, I'll be installing a cooler like I and RonD were talking about. And then pay attention to the transmission temps to see what happens then. Normal every day driving, it's been fine, even during the height of summer when I finally got around to properly setting up my ScanGaugeII to read transmission temperatures.
 

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