42RLE Transmission Temperatures?

Irun

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For those of you running a temperature gauge on your 42RLE, what temperatures do you normally see on the trail?
 
Desert SW. I have a Hayden aux cooler installed as well. 160 degrees is the highest I’ve seen on mine.

My temp sensor is located on the output of the aux cooler......so the hot fluid from the transmission goes through the stock radiator cooler first, then the aux cooler then it hits the temp sensor.
 
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Desert SW. I have a Hayden aux cooler installed as well. 150 degrees is the highest I’ve seen on mine.

I've seen as high as 165°, but am wondering about the sensor placement.
 
My previous 03 Rubicon ran around 180-190 measured at the inlet of the factory tranny cooler. That was with the largest tube/fin cooler I could fit in front of the A/C condenser. I also had a temp sender installed in the tranny pan and it typically ran around 150-160. While the pan temps were pretty stable it was common to see line temps vary by as much as 30 degrees depending on whether on not the converter was locked.
 
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Slightly over 180* while driving through deep loose sand on the beach and connecting roads. Slightly less than that when sitting for a while idling in July/August heat. 160* when driving Normal roads in July/August heat.

my sensor is in the pan.
 
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While I don't have a gauge on mine it used to go into first stage overheat on hot days on the trail. That's an internal transmission temperature of over 240. The pan temperature was probably near that. The first stage overheat is pretty obvious if you are paying attention, delayed shifts and early lockup. The transmission will feel like it is sticking in gear longer than normal. Since adding a cooler it hasn't been hot enough to go into the overheat shift schedule again.
 
Slightly over 180* while driving through deep loose sand on the beach and connecting roads. Slightly less than that agent sitting for a while idling in July/August heat. 160* when driving Normal roads in July/August heat.

my sensor is in the pan.

Thanks Tom! My sensor is in the pan as well. The highest temperatures I've seen thus far is 166°, during a summer wheeling trip.
 
Bumping up this old thread to see what is normal when crawling in 4high and 4 low.

I got a pan temp sensor installed in my pan and I was able to get it up to 170/180 with Highway and then straight to some slow 2 high off-road. Temp dropped back down when driving on cities roads back home.

I have a new mopar radiator but no auxiliary cooler, hoping I don’t need one but I often do trail runs where I’m in 4 high and 4 low
 
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While I don't have a gauge on mine it used to go into first stage overheat on hot days on the trail. That's an internal transmission temperature of over 240. The pan temperature was probably near that. The first stage overheat is pretty obvious if you are paying attention, delayed shifts and early lockup. The transmission will feel like it is sticking in gear longer than normal. Since adding a cooler it hasn't been hot enough to go into the overheat shift schedule again.

Since this got bumped, I'm gonna pull at this thread a little. I definitely know more about the 32RH than I do the 42RLE, but this seems to imply there is a temperature sensor in the 42RLE?? That would be brand new information (to me) and also unexpected. Also it's interesting that the response to high temps is to essentially increase RPM. I guess that's to increase circulation of hot fluid to lower the temperature? I would've guessed it would shift early to slow down the source of the heat.
 
Since this got bumped, I'm gonna pull at this thread a little. I definitely know more about the 32RH than I do the 42RLE, but this seems to imply there is a temperature sensor in the 42RLE?? That would be brand new information (to me) and also unexpected. Also it's interesting that the response to high temps is to essentially increase RPM. I guess that's to increase circulation of hot fluid to lower the temperature? I would've guessed it would shift early to slow down the source of the heat.

Not that I’ve found through my hours of research. And if there is you have to buy a very expensive scan tool to access that info, still a big if.

If there was a senor, I don’t think guys like MrBlaine would recommend the transmission pan temp senor install.

If possible let’s keep this thread to what others are seeing as far as temps go, I tried to not start another thread to see if we could keep this one going on topic
 
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Bumping this up again because I’m about to head out and try some rock crawling in warm/hot ambient temps.

From my research people are saying the manuals says 150-200 is normal. But at what point do you need to stop and try to cool it down?

And how do you cool the transmission temp down if you’re in the middle of a crawling trail that you are unable to get speed to get more air through the radiator? Stop and let it idle in N or P?
 
I see more temperature increase on the highway (on inclines), than I do on the trail.
I'm assuming the 4 Lo reduces the load on the transmission.
 
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I see more temperature increase on the highway (on inclines), than I do on the trail.
I'm assuming the 4 Lo reduces the load on the transmission.

Good to know! Mine doesn’t get much above 180 on the 10-15 mile hwy trips I’ve tested it. Basic off-roading (slower 4 high stuff) I’m around 180. This is all with a new mopar radiator recently installed (installed to fix coolant temps, not to fix transmission temps). Maybe I will get lucky and my new radiator will cool the teams sufficiently

I reached out to Blaine and he was saying 220-230 sustain is acceptable, ideally he would like to see it lower.

I should get to do some 4H and 4L rock crawling in the next week or so, I will report back with temps I see
 
Since this got bumped, I'm gonna pull at this thread a little. I definitely know more about the 32RH than I do the 42RLE, but this seems to imply there is a temperature sensor in the 42RLE?? That would be brand new information (to me) and also unexpected. Also it's interesting that the response to high temps is to essentially increase RPM. I guess that's to increase circulation of hot fluid to lower the temperature? I would've guessed it would shift early to slow down the source of the heat.

Yes, there is a temperature sensor in all 42RLEs, TJ and JK ones as well. It is in the valve body. Basically it reads almost the same temperature as in the bottom of the pan. The reason why I say almost - bottom of the pan is cooled down by air, and as a result will be a little cooler than the space on top of the valve body bottom plate. The sensor outputs the signal to through the connector on the driver side, where the shift column is. Information that flows through this connector is - temperature and shifter position (user input, when you move the handle in the cabin, it turns the column, and column had a way to report which gear was selected). TCM (in 2003 or 2004) or PCM (in 2005 to 2006) uses these inputs (together with input and output speeds) from the transmission itself in addition to inputs from PCM (throttle position and RPM) to decide on commands that it sends to solenoid pack, through the connector on the exhaust side. If you put reverse, park or neutral, it does not send any commands to solenoid, keeping it default all open and flow of oil is regulated only by the manual valve. if you put into drive, then default is 2nd gear (which is what happens when you are in limp mode - TCM failed to control the solenoid pack and drive simply means 2nd gear) then the TCM starts to work, and starts shifting between 1 to 4 using the solenoid pack to control the flow of oil to the right pistons.
I thought about hacking into this wire, measuring it with scope, and the doing a hack in sensor, but then decided that unlike data wires, this is analog signal, in which a voltage level is what carries the data (not 1 and 0 encoded, but rather a continuous range of voltages to indicate temperatures), so hacking into the line might compromise it and screw up the way TCM makes shift decisions - they depend on temperature - TCM shifts differently when cold and when hot.
 
Yes, there is a temperature sensor in all 42RLEs, TJ and JK ones as well. It is in the valve body. Basically it reads almost the same temperature as in the bottom of the pan. The reason why I say almost - bottom of the pan is cooled down by air, and as a result will be a little cooler than the space on top of the valve body bottom plate. The sensor outputs the signal to through the connector on the driver side, where the shift column is. Information that flows through this connector is - temperature and shifter position (user input, when you move the handle in the cabin, it turns the column, and column had a way to report which gear was selected). TCM (in 2003 or 2004) or PCM (in 2005 to 2006) uses these inputs (together with input and output speeds) from the transmission itself in addition to inputs from PCM (throttle position and RPM) to decide on commands that it sends to solenoid pack, through the connector on the exhaust side. If you put reverse, park or neutral, it does not send any commands to solenoid, keeping it default all open and flow of oil is regulated only by the manual valve. if you put into drive, then default is 2nd gear (which is what happens when you are in limp mode - TCM failed to control the solenoid pack and drive simply means 2nd gear) then the TCM starts to work, and starts shifting between 1 to 4 using the solenoid pack to control the flow of oil to the right pistons.
I thought about hacking into this wire, measuring it with scope, and the doing a hack in sensor, but then decided that unlike data wires, this is analog signal, in which a voltage level is what carries the data (not 1 and 0 encoded, but rather a continuous range of voltages to indicate temperatures), so hacking into the line might compromise it and screw up the way TCM makes shift decisions - they depend on temperature - TCM shifts differently when cold and when hot.

Good info! Long story short, if you want a transmission temp gauge, gotta install an aftermarket one in the pan :)
 
as an engineer dealing with complicated electronics for living, I have to say that it is possible to create a tap into this line, but this has to real automative quality device, that has to meet all the quality requirements for this. Unlike all the OBD junk, which has 0 chances to mess up the propulsion, tapping into TCM Lines might have propulsion impact, and as a result I would not do it, unless I invest plenty of money in testing and manufacturing quality for this
 
Seems like the 42rle likes to run hot.
I suggest you add an aux. cooler.
IMO, larger tires on stock gears can also add to trans.issues.

What temps do you usually see with a cooler? Do you have any data before installing the cooler?
 
Good info! Long story short, if you want a transmission temp gauge, gotta install an aftermarket one in the pan :)

yes, this is what I did. It is not exactly the same temperature as TCM will see it (especially at highway speeds - pan sensor will underreport the actual temperature due to being cooled by external air), but when crawling or on slow trails or traffic jam, it will be damn close.
 
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