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Discussion Starter · #1 ·
I've been doing some research on the "Hot Oil" message on my dash. It always comes on when I'm in 4hi or 4lo for more than 30 minutes. After reading multiple threads from here and different forums, I learned that I will need a transmission cooler so I don't tear up the transmission. My question is do you know of any good coolers? How much do they run? Easy I install or should I have a mechanic do it? I have a 2007 automatic by the way.
 

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I have had great luck with tru-cool tranny coolers. They are thermal bypass coolers meaning that they bypass the cooler until the fluid comes up to temp. This is a great feature if it gets cold where you live.
 

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Rather than discussing brands, everyone has a favorite, I would suggest you do a Google search and look for a thermostatically controlled transmission cooler. Then decide on a unit that will fit your Jeep. You want your transmission fluid to reach operating temperature quickly and then have the temperature controlled once it gets there. Installation is pretty straight forward, and depends on your mechanical ability. It is certainly a job most DIY people can tackle easily.
 

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If the Hot Oil comes on reproducibly like that, I would not rush to install a cooler. It's like trying to cure The Death Wobble by steering stabilizer: completely fails to address the problem.

Instead, I would investigate the stock heat exchanger first. Perhaps a line is kinked or otherwise plugged. Verify that T-case has enough ATF in it, perhaps it gives off extra heat through common wall when in low.

The 42RLE we have on pre-Pentastar JKs varies in quality. Some of them heat up, some don't. Mine is fine, I wheel it hard in 110 degree heat by crawling and nothing happens to it (I had the Hot Oil recall done, so the signal is there). It tells me that the basic design is okay. If you got a duff unit, it's not okay.
 

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If the Hot Oil comes on reproducibly like that, I would not rush to install a cooler. It's like trying to cure The Death Wobble by steering stabilizer: completely fails to address the problem.

Instead, I would investigate the stock heat exchanger first. Perhaps a line is kinked or otherwise plugged. Verify that T-case has enough ATF in it, perhaps it gives off extra heat through common wall when in low.

The 42RLE we have on pre-Pentastar JKs varies in quality. Some of them heat up, some don't. Mine is fine, I wheel it hard in 110 degree heat by crawling and nothing happens to it (I had the Hot Oil recall done, so the signal is there). It tells me that the basic design is okay. If you got a duff unit, it's not okay.
Good point on checking the fluid but I would and did install a aux cooler for peace of mind and also from seeing the craptastic stock cooler design. It is like 2 rows in the AC condenser.

With my cooler installed it stays at a nice 110-120 degrees. Well worth the minimal cost to me.

FYI I installed the B&M super cooler 70268
 

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Rather than discussing brands, everyone has a favorite, I would suggest you do a Google search and look for a thermostatically controlled transmission cooler. Then decide on a unit that will fit your Jeep. You want your transmission fluid to reach operating temperature quickly and then have the temperature controlled once it gets there. Installation is pretty straight forward, and depends on your mechanical ability. It is certainly a job most DIY people can tackle easily.
^^^This......:thumb:
 

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Discussion Starter · #7 ·
If the Hot Oil comes on reproducibly like that, I would not rush to install a cooler. It's like trying to cure The Death Wobble by steering stabilizer: completely fails to address the problem. Instead, I would investigate the stock heat exchanger first. Perhaps a line is kinked or otherwise plugged. Verify that T-case has enough ATF in it, perhaps it gives off extra heat through common wall when in low. The 42RLE we have on pre-Pentastar JKs varies in quality. Some of them heat up, some don't. Mine is fine, I wheel it hard in 110 degree heat by crawling and nothing happens to it (I had the Hot Oil recall done, so the signal is there). It tells me that the basic design is okay. If you got a duff unit, it's not okay.
I'm going to check all the fluid levels and still get a cooler just in case

Good point on checking the fluid but I would and did install a aux cooler for peace of mind and also from seeing the craptastic stock cooler design. It is like 2 rows in the AC condenser. With my cooler installed it stays at a nice 110-120 degrees. Well worth the minimal cost to me. FYI I installed the B&M super cooler 70268
I'm looking at the B&M one you have and this one http://www.4wheelparts.com/Heating-..._c=84&t_s=518&t_pt=3660&t_pn=R/M07133638TRANS
 

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I'm going to check all the fluid levels and still get a cooler just in case


Synthetic oil is good up to approx. 400 degrees, before it will break down. So the issue isn't the oil, but rather the clutch packs running hot. They don't hold up very well with ongoing high temperatures.

So check your levels first, and also make sure that the oil doesn't smell burnt, (from the clutch packs). If it does, then I would have the transmission oil changed, along with the filter.
But yes, installing a oil cooler, will be a major plus..........:thumb:
 

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I'm not really sure what the difference is between the 2
The B&M is a better stacked plate design with a low flow bypass. Much more efficient than the tube and fin design of the other at half the cost.

If you Google "jk trans cooler" jk-fourm has a good write up and that's how I installed mine. Been great for over a year. Easy install too, only took a couple of hours.
 

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Synthetic oil is good up to approx. 400 degrees, before it will break down. So the issue isn't the oil, but rather the clutch packs running hot. They don't hold up very well with ongoing high temperatures.
Pardon my ignorance, but aren't clutch packs running hot only if they slip? How much heat do solenoids generate at all? I thought it was insignificant, tens of Watts at the most.

I forgot to mention that I flushed the factory ATF as soon as I got the jeep home back in 2010 and filled with Valvoline synthetic.
 

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Get the B&M super cooler. Installs easily. I like the internal thermostat that will bypass the cooler until the fluid warms up. My 2009 never had a problem, but it is a know problem from 07 through 09. Why take the chance of burning up your tranny when there's a $80 solution.
My kit came with some hose a brass connector and hose clamp. I need to get an extra 2ft of hose another brass connector and clamp.
 

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Discussion Starter · #14 ·
Just ordered the B&M super cooler. Great reviews, low price and pretty straightforward install
 
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