Where to install transmission temperature sender?

[thomat65]

I'm thinking about installing a temperature gauge for the 42RLE in my 04. I've heard people argue three different ways about where it should go. So I want to see what you guys recommend.

But I also want to understand why. What part of the transmission (fluid is a part too) is most sensitive to heat? Is that even the right question for me to ask?

 

[Irun]

https://transmissioncoolerguide.com/best-transmission-temperature-gauges/

 

[mrblaine]

I'm thinking about installing a temperature gauge for the 42RLE in my 04. I've heard people argue three different ways about where it should go. So I want to see what you guys recommend.

But I also want to understand why. What part of the transmission (fluid is a part too) is most sensitive to heat? Is that even the right question for me to ask?

The correct location is based on the correct question. What do you want to know? What you want to know is how hot is my transmission? The place that gives you that answer is in the pan.

If you place it in the line going to the radiator, you are reading the fluid temp after it leaves the place where it gets the hottest and that is from the work it has done in the torque converter. Trying to extrapolate anything from there is the equivalent of putting a temp sensor in the combustion chamber of the engine where it is the hottest and then trying to figure out how hot the engine is running.

Putting it in the line from the radiator gives you a false reading since that doesn't tell you how hot the trans is running.

 

[thomat65]

The correct location is based on the correct question. What do you want to know? What you want to know is how hot is my transmission? The place that gives you that answer is in the pan.

Yeah that's the question behind my question: what do I really need to know?

@Irun's link says basically the same thing as you're saying: "[Putting it in the pan] provides you with an accurate temperature reading of the fluid that returns to the transmission after flowing through the cooler. Overall, this mounting location will give you the most accurate average reading of the trans fluid." I get the logic: do you want to know how hot your transmission is or not?

But other things I'm reading point to the need to know how hot the transmission fluid is (until temperatures get hot enough to begin directly affecting seals and clutches or turn your TC blue). The logic behind that thinking seems to be: heat is the indirect cause of a damaged transmission; a more direct cause is burnt transmission fluid (which stops lubricating). In other words: are you burning your transmission fluid?

So if I want to know how hot the seals and clutches in my transmission are then it makes sense to me to put the sender as close to them as possible. But is it more useful to know fluid max temp?

Since I'm already overthinking this I'll also ask: does it really matter if the transmission fluid is super hot if it's only that temperature for a short time (i.e. on its way to the cooler)? My experience burning everyday objects tells me it's a function of time. If it doesn't matter then maybe the prize money should go to the location with the best representation of average temperature.

Maybe if I'm that worried about it I should just install two senders and a switch!

 

[AndyG]

I put over 440,000 miles on a stock automatic transmission that towed heavy loads.

If you’re concerned about longevity this is what I recommend:

Run a good aftermarket cooler

Change the fluid the filter don’t let someone just hook it up to a machine that circulates fluid out of it because the filter eventually will clog and become in efficient and cause overheating

Don’t dog it or back up and go from reverse to drive while it is still rolling backward

Turn the overdrive off whenever it is needed and if it’s the later model 42rle That is about all the time

Never change your avatar

 

[Jerry Bransford]

Don't make this any more difficult than it needs to be, just install the sender in the pan and don't overthink this.

 

[AndyG]

Don't make this any more difficult than it needs to be, just install the sender in the pan and don't overthink this.

Jerry hath spoken. Thread closed.

 

[mrblaine]

Yeah that's the question behind my question: what do I really need to know?

@Irun's link says basically the same thing as you're saying: "[Putting it in the pan] provides you with an accurate temperature reading of the fluid that returns to the transmission after flowing through the cooler. Overall, this mounting location will give you the most accurate average reading of the trans fluid." I get the logic: do you want to know how hot your transmission is or not?

But other things I'm reading point to the need to know how hot the transmission fluid is (until temperatures get hot enough to begin directly affecting seals and clutches or turn your TC blue). The logic behind that thinking seems to be: heat is the indirect cause of a damaged transmission; a more direct cause is burnt transmission fluid (which stops lubricating). In other words: are you burning your transmission fluid?

So if I want to know how hot the seals and clutches in my transmission are then it makes sense to me to put the sender as close to them as possible. But is it more useful to know fluid max temp?

Since I'm already overthinking this I'll also ask: does it really matter if the transmission fluid is super hot if it's only that temperature for a short time (i.e. on its way to the cooler)? My experience burning everyday objects tells me it's a function of time. If it doesn't matter then maybe the prize money should go to the location with the best representation of average temperature.

Maybe if I'm that worried about it I should just install two senders and a switch!

Did you miss the part about putting a temp sender in the combustion chamber which is extremely hot when the gas/air mixture explodes to drive the piston down? You don't need to know that, you need to know how hot the engine is running, period. They don't put a temp sender in the top hose and one in the bottom hose and then one in the engine block so you can average all three, check for the delta between what each is doing, they put it where it gives them a relevant reading.

The same is true for the fluid in the pan. The trans operating temp and the pan temp are going to be close enough to tell you what you need to know. You don't need to know the temp of the fluid leaving the converter where it is the hottest since it is already very likely starting to cool down on the way to the radiator. The converter is trying to shear the fluid and it is the hottest right at that point which is also why it leaves there and gets circulated otherwise it could just be a close system.

All you need is how hot is my transmission and the place to get that is in the pan. Install 3 and a switch if you really want the max amount of useless info.

 

[never monday]

The temp of the oil in the pan is also telling you the temp of the oil your pump is about to suck up and spread thru the trans. You want to know if that oil is getting too hot to do it’s job.