2009 JK automatic tranny temp questions - JKowners.com : Jeep Wrangler JK Forum
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post #1 of 47 Old 05-17-2009, 07:37 AM Thread Starter
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2009 JK automatic tranny temp questions

What auto tranny is in the 09 JK?

What is the normal operating temp?

Is there a chart somewhere showing temp ranges?

Thanks all.
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post #2 of 47 Old 05-17-2009, 07:50 AM
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Do the jk auto have a stock tranny cooler?? My wifes 08 liberty has a tranny cooler. Would be a good benefit to add one to it if it doesnt.
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post #3 of 47 Old 05-17-2009, 08:22 AM
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Do the jk auto have a stock tranny cooler?? My wifes 08 liberty has a tranny cooler. Would be a good benefit to add one to it if it doesnt.
here is a quote from my service manual:
"The automatic transmission oil cooler is located in the front of the radiator and behind the front grill and is combined with the A/C condenser. The transmission oil cooler is a heat exchanger that allows heat in the transmission fluid to be transferred to the air passing over the cooler fins."

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post #4 of 47 Old 05-17-2009, 08:45 AM
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Originally Posted by JK Jim View Post
What auto tranny is in the 09 JK?

What is the normal operating temp?

Is there a chart somewhere showing temp ranges?

Thanks all.
don't know anything about the temps, even snooped the shop manual. according to jeep.ca the 09 still has the 42RLE 4spd auto.

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post #5 of 47 Old 05-17-2009, 09:03 AM
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yes its still the 42rle, and do yourself a favor and install some sort of aftermarket tranny cooler. The factory cooler is already built into the A/C condensor, is not very big, and it sits directly behind a crossmember, so it doesnt get much air flow. I was just putting around on some hunting trails last summer, and my temp gauge (I have a Interceptor Scan Gauge) was hitting 215*F. I believe the factory warning (the dreaded "ding") is set to come on at 230 or 240*F. Now this wasn't even out on a real trail, climbing rocks and really working it. It never dropped below 195*F until we got back out on the open road, and even then it took it awhile to start coming back down. Since then I installed a tranny cooler that my gf's dad gave me and I don't see temps above 180*F on those same trails.

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post #6 of 47 Old 05-17-2009, 12:57 PM
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These goddamn son of a *****in' transmissions run hotter than ****! Get a transmission cooler on there ASAP before you need to go spend a bunch-o-money at the dealership on it like I do.

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post #7 of 47 Old 05-17-2009, 01:46 PM Thread Starter
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Thanks for the replies. Now some additional questions:

What brand cooler is recommended for the JK?

Easy install?

Will this void my warranty? I don't want to give Chrysler a reason to void my lifetime powertrain warranty over this. That is if they'll even being honoring their warranties in the near future.
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post #8 of 47 Old 05-17-2009, 03:42 PM
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Is anyone out there doing anything to beef up the 42rle? Theres not a whole lot of options for clutches, torque converters, etc. that ive been able to find.


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post #9 of 47 Old 05-17-2009, 05:16 PM
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I tryed looking for different converters and deeper pans and came up with nothing. There might be some companies that make shift kits or stuff to update the valve body, but there nothing for them performance wise. I think the heat that these things generate are part of the reason the program them to lock the tc clutch up so early.

Most guys like to use the B&M coolers. 70268 is the one I think most use on the JK's. They're a nice, rugged cooler. Only reason I used the cooler I did is cause my gf's dad had a brand new one laying around and gave it to me. In the end, I should have just gone with the b&m cooler, I wound up spending about the same money just in hoses and fittings trying to adapt the powerstroke cooler to work, and I had to fab up a mounting bracket for it as well.

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post #10 of 47 Old 05-17-2009, 05:18 PM
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Oh, and I don't think you really need to bother with the more expensive cooler kits that come with the electric fan. I went wheeling at Rausch Creek, and I never had the tranny temp get too high. Besides, a quick blast through some fender high water cools em down real quick

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post #11 of 47 Old 05-17-2009, 06:46 PM
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Quote:
Originally Posted by afoulk View Post
Oh, and I don't think you really need to bother with the more expensive cooler kits that come with the electric fan. I went wheeling at Rausch Creek, and I never had the tranny temp get too high. Besides, a quick blast through some fender high water cools em down real quick
Come to the high desert young man.

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post #12 of 47 Old 05-18-2009, 06:28 AM
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Without a tranny temp gauge you don't know if the the tranny needs additional cooling. That said with a cooler my tranny never gets above 130įF on the freeway, and the highest I've seen it off-road is 165įF.

Transmission Cooler
https://www.jkowners.com/forum/showthread.php?t=2458

Transmission Temp Gauge
https://www.jkowners.com/forum/showthread.php?t=3784

Here's the tranny fluid level vs temp fill info:

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post #13 of 47 Old 05-18-2009, 07:45 AM
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here's a question. Since the cooler is combined with the A/C condensor. Wouldn't running your A/C on max help to cool the trans? I have never gotten the dreaded "ding" and I have wheeled in very HOT conditions. But I always have the jeep running with the A/C blowing cold because my kids are always sitting in the back seat. Even when we are waiting in line at an obstacle, most times my A/C is running at full.

So would the A/C condensor provide some cooling affect?
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post #14 of 47 Old 05-18-2009, 09:32 AM
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Just the opposite. That is where the heat from inside the vehicle is released. The refrigerant is compressed which makes it hot, and then bleeds off its heat in front of the radiator to the ambient air. The refrigerant then flows to the heat exchanger inside the cabin and is allowed to expand which makes it get cold. It absorbs the heat from the cabin and and goes back to the compressor to finish the loop.

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post #15 of 47 Old 05-18-2009, 09:33 AM
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Just the opposite.
X2 Ever notice the radiator fan come on when the a/c is running? That's because it needs additional cooling.
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post #16 of 47 Old 05-18-2009, 10:28 AM
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I had lots of overheating problems before then, and eventually it failed on me. I now have a brand-new transmission, and went ahead and installed an aux. cooler (just an inexpensive flex-lite) - and surprise surprise, that sucker is HOT compared to the stock cooler. Which means its dissipating a lot more heat.

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post #17 of 47 Old 05-18-2009, 08:00 PM Thread Starter
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Any dealership personnel on the forum who can answer the question about installing an aftermarket tranny cooler and voiding the warranty?
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post #18 of 47 Old 05-19-2009, 04:55 AM
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Quote:
Originally Posted by JK Jim View Post
Any dealership personnel on the forum who can answer the question about installing an aftermarket tranny cooler and voiding the warranty?
As always Magnusson Moss applies. The dealership needs to prove that your modification caused the warranty issue.
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post #19 of 47 Old 05-19-2009, 05:05 AM
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PhilD, did you ever do a test with your gauge and the A/C? I assumed the same thing, but I have read other post that stated when they tuned on their A/C the temp dropped. Maybe it dropped because when you turn on the A/C the computer will turn on the fan, and with the fan running you'll get more air flow to cool the transmission - which does make some sense. I don't have a gauge, so I can't test it myself.
I have an external cooling and I can't see any difference when turning the AC on. At highway speeds I wouldn't expect to, and at slow speeds I'd expect any additional cooling from the airflow to be negated by the heat exchange between ac and trans coolers.

Maybe in a cold climate where the ac system was not generating much heat it may work, but it seems a clumsy way of turning the fan on. An additional cooler does the job so much better and is easy enough to add.


Quote:
I have also read the running in 4LO will cool down the transmission. Again, since I donít have a gauge I canít confirm that either.
Not sure why. I can say that the hottest trans temps I've seen have been in 4Lo, when you are moving very slow with little airflow, and working the trans hard.
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post #20 of 47 Old 05-19-2009, 06:36 AM
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Not all true I have the Hayden 404 Trans Cooler On 05/03 pulling my 18' Camper on the way home from a wheeling

trip about 250 miles from home doing 65 mpg with the OD off my temp went up to 250F I was driving in to a strong head wind and the Jeep kept down shifting I had no bells or lights come on and the stock gauge was at the white line to the right of half and I got the temp from my Scangauge ll 250F so I had to shut off my AC

and slow down to 60 for my temp to come down. My Hayden 404 Trans Cooler is ment for towing 5,500 lbs.

I have had my Jeep at the dealer many times to say my Jeep runs hot (even before I did the Trans cooler) And they said even after a hour drive hooked up the the computer that my temp is in normal range! I said on the road not towing It will go up to 222f and back down and they still say that is normal... So you tell me?

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post #21 of 47 Old 05-19-2009, 06:45 AM
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So you tell me?
You are talking about water temp, we are talking about trans temp, but your experience with having to shut off the ac to help cool things down would be the more logical effect of having the ac on, ie: things get warmer.

FWIW My WT gets up to 220įF and I consider it normal, as long as it doesn't stay there. However, I would not consider 250įF normal, nor would I be happy with it, towing or not.
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post #22 of 47 Old 05-19-2009, 08:00 AM
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Quote:
Originally Posted by joe002 View Post
The fan coming on will definitely cool the transmission more than no fan, however I have no idea how much extra cooling you get.
But with just the stock cooler in the ac stack you have to figure that some of the heat generated by the ac cooler will get transferred to the trans cooler. Like I said maybe when it's cold outside it may help, but it seems an unreliable way of trying to cool the trans.


Quote:
The only explanation about 4LO cooling things off better that I could cope up with is that since the transmission is working harder it may pump the transmission fluid faster/harder though the radiator thus cooling things off better
When the trans works harder it generates more heat not less. The engine rpm would be higher, but I'm not sure the trans will be pumping any more fluid around. My own observations show that the trans is coolest when on the highway in 3rd or 4th when the TC is locked, and hottest when in 4Lo on the trail when there is lots of TC slippage and a lot of heat generated.
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post #23 of 47 Old 05-19-2009, 08:12 AM
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Quote:
Originally Posted by joe002 View Post
The only explanation about 4LO cooling things off better that I could cope up with is that since the transmission is working harder it may pump the transmission fluid faster/harder though the radiator thus cooling things off better Ė kinda like the water pump turns at the speed of the engine (as the engine turns faster the water pump turns faster). I donít know if the transmission oil pump pumps faster/harder when itís working harder?
The trans pump is splined by the torque converter hub; which in turn is bolted to the crankshaft via the flexplate. So, yes, the pump is engine-RPM sensitive. However, I believe that this trans has a variable line pressure solenoid that controls maximum line pressures, anyhow.

Most of the trans heat is generated by the torque converter at low RPM's/speed due to the internal "slippage" of the design of the torque converter and lesser air flow through the radiator. I always recommend an external trans cooler (preferably B&M or similar design - I don't like the "tube and fin" type coolers). The ideal temp for most autos is around 180 give or take 10 degrees. The problem with the stock-in-the-radiator cooler is that not only is it small, but it will never get cooler than its surroundings. The surroundings being the engine coolant which runs anywhere from 200 to 225 - not good for the trans.

I don't claim to be an expert on the 42RLE, but I did spend 14 years as a GM transmission specialist; so, I do know something about auto trannies in general.
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post #24 of 47 Old 05-19-2009, 08:19 AM
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Someone recommend a cooler for me (links would help). And how difficult to install?
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post #25 of 47 Old 05-19-2009, 08:25 AM
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Quote:
Originally Posted by Ogie View Post
The trans pump is splined by the torque converter hub; which in turn is bolted to the crankshaft via the flexplate. So, yes, the pump is engine-RPM sensitive. However, I believe that this trans has a variable line pressure solenoid that controls maximum line pressures, anyhow.
Not sure about the line pressure, but yes the TC drives the pump. Engine rpms when in 4LO are rarely that high, and the amount of heat generated by the TC far outweighs any potential extra cooling from a faster pump rate.

The TCM will switch on the fan if the trans temp gets out of range.


Quote:
The problem with the stock-in-the-radiator cooler is that not only is it small, but it will never get cooler than its surroundings. The surroundings being the engine coolant which runs anywhere from 200 to 225 - not good for the trans.
The stock cooler is in front the of the main radiator, so when on the highway it works quite well, but as you mentioned, when airflow is slow, ie: when in 4LO, the whole area is going to get hot. the fan will obviously help, but I think it's safe to say that the trans will likely get hotter when in 4LO.


Quote:
I don't claim to be an expert on the 42RLE, but I did spend 14 years as a GM transmission specialist; so, I do know something about auto trannies in general.
Always good to have people here that know what they are talking about


Do you have any suggestions on what to do about the fluid pickup sucking air on steep declines and losing tranny pressure?
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