Installing a Jeep Transmission Cooler

When it comes to automatic transmissions, heat is your worst enemy. Like many Wranglers with automatic transmissions, my 2005 Jeep had the transmission cooler build into the bottom of the radiator. What this means is that as I drive, the automatic transmission will build up heat – transmission fluid will carry this head through hoses to the radiator, where it runs through a small cooler. The engine fan helps force air through the cooler, cooling the transmission fluid, and bringing it back to the automatic transmission.
The problem with this setup is that the stock cooler can sometimes be undersized, especially if you do any towing with your truck. I decided that it would be best to add a second transmission cooler, installed before the stock one. The overall process in installing an additional cooler is to mount the transmission cooler, then splice into the line going to your stock cooler.


Stock Setup:
This is the stock Wrangler (TJ) radiator. Notice the two supports in a V shape – we’ll be using them to mount the transmission cooler to.

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B&M transmission cooler:
I choose the B&M 70255 transmission cooler which turned out to be a perfect fit (they cost around $50 at amazon.

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The kit comes with hoses, barbs, and an array of hardware. This was more than enough to mount the cooler.

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Mounting the cooler:
The cooler will slide in through the driver side headlight. To make this tight fit happen, we start by removing the headlight.
First, unplug the headlight

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Remove the trim ring, then remove the three screws that hold the headlight in place

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If you fold back the rubber flap you are able to see how we’ll insert the transmission cooler

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Just hold the flap back as you insert the transmission cooler.

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Now we’re ready to mount the cooler. The first thing to make note of is the position of the input and outputs on the cooler. You’ll want these to be either up, or on the side – if you put the inputs on the bottom then the cooler will fill with air, preventing it from doing it’s job. Once you have the transmission cooler positioned correctly, Just run to heavy duty zip ties through the bottom two mounting holes, anchoring it to the radiator supports.

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This part may take a bit of trial and error. With the lower trans cooler mounts in place, use the supplied metal rods, bending them into a shape that will allow you to connect one end to the transmission cooler, and the other end to a hole drilled in the flat metal next to the radiator. I went ahead and painted the metal rods to prevent rust.
Left upper transmission cooler mount:

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After bending the mount, I then drilled a hole into the horizontal metal next to my Jeep’s radiator.

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Then I connected the left trans cooler support, and did the same thing for the right upper support.
Here you can see the trans cooler mounted

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Plumbing the Jeep transmission cooler
The last thing to do is plumb the tran cooler into your automatic transmission fluid system. This sounds harder than it is – all you really need to do is find the input to your stock trans cooler, cut it, and splice in the new cooler. Be careful to route your lines where they are out of the way, and won’t hang down to snag on anything.
I started by connecting hoses to the cooler and routing them down

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I cut the driver side line going to my stock transmission cooler, and connected the new hoses. The connector that I used just had hose barbs on each side.

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Once the lines were connected I secured them with zip ties, making sure to route them where they would be safe.

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That’s it. Be sure to check for leaks the first couple of times you drive. Your transmission should last quite a bit longer now that it won’t overheat as easily.