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I had read this thread a while back and a it was mentioned that the 42RLE had a factory sensor, but nobody knew if it could give an actual temp reading. I had a Snap-On Ethos hooked up to my TJ today and it could tell me the actual temp. It said 122 F, which seemed right for the conditions. Not sure how to make it work with a gauge, but I thought I would mention that it can give an actual temp.
 

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That is precisely what I was wondering about the past few days due to the JK 42RLE recall that enables the display to show "Hot Oil" when the tranny overheats.

Thanks for your testing.

I've got this to install after I verify it can get a reading from the trans sensor...


But I can't figure out the best place to install it in this...



:confused:

Mine doesn't have power windows, so the area between the two center air vents is available, but I've got to get out there tomorrow afternoon and measure and see if my gauge will fit between them. What do you think?
 

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I had read this thread a while back and a it was mentioned that the 42RLE had a factory sensor, but nobody knew if it could give an actual temp reading. I had a Snap-On Ethos hooked up to my TJ today and it could tell me the actual temp. It said 122 F, which seemed right for the conditions. Not sure how to make it work with a gauge, but I thought I would mention that it can give an actual temp.
My Snap-On Modis also displays the trans temp.
The voltages vs.temps are listed on the Snap-On Shop Key, problem is finding a compatible aftermarket gauge to tap into it with..
that is something unlimited04 had been researching as well.
 

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My Snap-On Modis also displays the trans temp.
The voltages vs.temps are listed on the Snap-On Shop Key, problem is finding a compatible aftermarket gauge to tap into it with..
that is something unlimited04 had been researching as well.
the snap-on thing may be accurate, especially if you're plugging it into the OBDII port. My ScanGauge isn't able to read trans temp, and I've sent some info to ScanGauge (the company) and they are supposedly working on getting the XGauge protocol to read trans temp....but no timeline. With OBDII, you need to know what protocol to use to get into the TCM...since trans temp is stored in the TCM, NOT the PCM. Noone that I know of has been able to crack that...besides the StarSCAN at the Chrysler dealership.

Maybe Snap-On has, or is using StarSCAN protocol or something. I wouldn't be surprised if Snap-On leased the technology from Chrysler or something along those lines.

The problem with using an aftermarket gauge is they don't work on the same temperature-voltage specs. The stock sensor is a dual range trans temp sensor, so basically you need digital handling to deal with the non-linearity:



To add an aftermarket trans temp gauge & sensor usually requires cutting into the hard trans lines, means you need to flare them....unless you use this: http://www.jeepforum.com/forum/f130/no-modification-auto-trans-temp-sensor-adapter-977088/

Check out jeep2008's gauge :shhh:
http://www.jeepforum.com/forum/f9/my-jeep-pics-my-little-mods-so-far-584434/index19.html#post8632152
 

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The problem with using an aftermarket gauge is they don't work on the same temperature-voltage specs. The stock sensor is a dual range trans temp sensor, so basically you need digital handling to deal with the non-linearity:
Exactly my point:2thumbsup:
 

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Unlimited04 decided to pee in my cheerios today... :laugh:

If a person was on the fence trying to decide to add an aftermarket B&M fan cooled trans cooler to the 42RLE, the OEM trans temp sensor issue would prompt them to go ahead with the aftermarket cooler and plumb an aftermarket temp sensor in with the B&M to run the AutoMeter gauge wouldn't it? :ballchain:
 

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Unlimited04 decided to pee in my cheerios today... :laugh:

If a person was on the fence trying to decide to add an aftermarket B&M fan cooled trans cooler to the 42RLE, the OEM trans temp sensor issue would prompt them to go ahead with the aftermarket cooler and plumb an aftermarket temp sensor in with the B&M to run the AutoMeter gauge wouldn't it? :ballchain:
well the way the trans lines are connected to the radiator & stupid plastic fittings makes a cooler a pain in the butt. on a TJ, there are no NPT fittings you can just thread in or out...i'm sure a JK is similar. so you end up cutting the soft line and splicing in the trans cooler. there are arguments for doing it on both the return side or inlet side of the radiator. i'd go return side...the 42RLE runs hot in extended mixed city/highway according to my gauge (190*F+), and very close to "Overheat mode" in the mountains, and if you're towing it would certainly be over 220-240*F, maybe even into "Super Overheat Mode" :brickwall.

thats why a sensor that doesn't cut into the hard lines is nice...less plumbing and less BS, plus still accurate enough.
 

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well the way the trans lines are connected to the radiator & stupid plastic fittings makes a cooler a pain in the butt. on a TJ, there are no NPT fittings you can just thread in or out...i'm sure a JK is similar. so you end up cutting the soft line and splicing in the trans cooler. there are arguments for doing it on both the return side or inlet side of the radiator. i'd go return side...the 42RLE runs hot in extended mixed city/highway according to my gauge (190*F+), and very close to "Overheat mode" in the mountains, and if you're towing it would certainly be over 220-240*F, maybe even into "Super Overheat Mode" :brickwall.

thats why a sensor that doesn't cut into the hard lines is nice...less plumbing and less BS, plus still accurate enough.
I agree with all of that. That was primarily the factor pushing me towards an aftermarket cooler with fan. I drive in all of those conditions you listed and I'm wanting to make an attempt at getting those trans temps under better control.

The '08 JK of mine does have a lifetime powertrain warranty, but I don't want to have to have the tranny swapped/rebuilt due to premature failure due to constant overheating. I'd really like to keep the stealerships hands off of it as much as I can. :laugh:

Your information on the factory trans temp sensor is helping push me to the conclusion that the added cooler/fan in addition to a standard aftermarket trans temp sensor is the best route to take. My plan was to plumb it into the factory soft lines, and put the trans temp sensor plumbed to the added cooler/fan.
 

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Today i went in an off road trip with a couple of my friends.The Jeep was, for the 5 hours duration of this ride,half the time in 2H and half the time in 4H.But we were moving really slow cause the trail ride was new and really narrow.Anyway shortly after we started i had my trans at the 2 or sometimes the 1 position and the gauge showed this



After half an hour it went there



It stayed there all the time we were moving slow and only when we drove in dry roads for 12-15 minutes, between trails ,a little faster than the 5-10 miles we were moving all day, it came a little down.Also when we stopped for half an hour for a brake it really cooled down but for the rest of the day it was that high.Any thoughts?
 

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was the sensor wet from snow or mud? was the needle bouncing?

if no to both...then its time for a transmission cooler...you were definitely in "Overheat Mode" at those temps....did you notice any difference in shifting?
Unfortunately neither the sensor was wet nor the needle was bouncing :(
I had the trans at 1 or 2 so not much shifting was happening.
Do you have any suggestions for an easy to fit reliable cooler?:cheers2:
 

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Do you have any suggestions for an easy to fit reliable cooler?:cheers2:
I have this one, but have yet to install it:
Derale transmission fluid cooler,Automatic transmission fluid cooler

reluctant to install it since to do it right you need to pull the radiator out, or at least away from the radiator support. Its like 3/8" too fat to slide in without undoing the radiator. I plan to install it on the radiator support using P-clip tabs, like a V8 ZJ's tranny cooler does: ZJ Grand Cherokee Transmission Cooler Install How-to from KOR!. Turns into a big project.

Stu on the subject: Automatic Transmission Cooler - 2
 

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I have this one, but have yet to install it:
Derale transmission fluid cooler,Automatic transmission fluid cooler

reluctant to install it since to do it right you need to pull the radiator out, or at least away from the radiator support. Its like 3/8" too fat to slide in without undoing the radiator. I plan to install it on the radiator support using P-clip tabs, like a V8 ZJ's tranny cooler does: ZJ Grand Cherokee Transmission Cooler Install How-to from KOR!. Turns into a big project.

Stu on the subject: Automatic Transmission Cooler - 2
Why put it in the grill?
 

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In the grill for me, but what's the best way to mount the cooler:

Side ways, fitting side down or fitting side up (fluid would drain down first)?
 

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In the grill for me, but what's the best way to mount the cooler:

Side ways, fitting side down or fitting side up (fluid would drain down first)?
I would let fluid line routing dictate the direction I mounted it. I think it'll be easiest that way. Since it's a pressurized line, the direction of the fittings should not matter.
 

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I just changed the fluid in my tranny. While I had the pan out I drilled it and put in a Summit drain plug kit for about $6 bucks. It had an 1/8" npt thread for the plug. I bought an Auto Meter trans temp gauge and screwed the sending unit into the drain plug bung. It works great. Reads about 130 degrees in stop and go traffic. It took all of about an hour start to finish. I know a lot of guys like to run the sending unit in the cooler line but the pan was good enough for me and it seems to be pretty accurate.

I have a B&M cooler and remote filter kit. As soon as I install it I'll post a write up. Still haven't decided where to mount everything.
 

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I just changed the fluid in my tranny. While I had the pan out I drilled it and put in a Summit drain plug kit for about $6 bucks. It had an 1/8" npt thread for the plug. I bought an Auto Meter trans temp gauge and screwed the sending unit into the drain plug bung. It works great. Reads about 130 degrees in stop and go traffic. It took all of about an hour start to finish. I know a lot of guys like to run the sending unit in the cooler line but the pan was good enough for me and it seems to be pretty accurate.
Good thinking! Next time I drop my pan I was going to put in a drain plug too. Thhis just gives me another reason to do it sooner. I already have a sensor in the cooler lines but was thinking of a Bransford dual sensor setup, with a switch to go back and forth.
 
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