Desert SW. I have a Hayden aux cooler installed as well. 150 degrees is the highest I’ve seen on mine.
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.
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.
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.
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.
Maybe I will get lucky and my new radiator will cool the teams sufficiently
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.
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.
Good info! Long story short, if you want a transmission temp gauge, gotta install an aftermarket one in the pan