Jeep Wrangler JK: How to Install Transmission Cooler

This article applies to the Jeep Wrangler JK (2007-present).

Your engine needs to be cooled to last and so does your automatic transmission. The factory runs the trans fluid through the radiator to cool it, but that does not always get the job done. You can perform a modification to your Jeep that will keep the transmission cool and make it last. An auxiliary transmission cooler is inexpensive and easy to install yourself. It will be one of the cheapest insurance policies you can get for your Jeep.

If you have heard about a TSB (Technical Service Bulletin) about the HOT light for the transmission coming on, don't get too excited. The TSB calls for installation of a factory designed trans cooler, but it is strictly for Wranglers sold internationally.

Step 1 – Remove grille

Remove the six plastic retaining screw/clips from the top of the grille. Figure 1 shows a plastic grille screw used prior to 2008. Screw it out as you pry the inside out. Then pull the clip out.

Figure 2 shows the clip used in 2008s and newer. Slip a flat screwdriver in the tangs to pop the center up and then pry out.

There are a number of plastic clips that hold the grille on at the bottom. To unsnap them just grab the grille near the bottom and pull forward. They will unsnap and then the grille can be pulled out.

Before you remove the grille, remove the turn signal bulbs by holding the lock in and then twisting them counter-clockwise. Set the grille aside.

Step 2 – Lay out trans cooler

There are a vast number of choices for trans coolers. The stacked plate design is what manufacturers use. Since B&M is a well-known brand, it's the example we will use.

Some are more specific to your application with the factory designed version being the best fit. It is two to four times as much money but should fit perfectly.

Be sure all of the parts are there before you start.

Step 3 – Attach mounts to cooler

Take the extra few minutes to mount the cooler correctly. Do it right the first time and you won't have to do it over.

The metal straps that bolt to the cooler to mount it to your Jeep are the way to go. By attaching one to each corner, the cooler will mount solidly. You can try to use existing holes in the Jeep but may need to drill a couple in the bottom grille brace. Allow an inch or so between the cooler and the radiator. Mock everything up before bolting anything on.

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When you are satisfied, tighten everything down.

Step 4 – Attach cooler hoses

Attach the ends of the supplied hose to the cooler with a hose clamp. Tighten with a 5/16" socket and ratchet. Run the hose under the bottom of the radiator or between the radiator and the grille support on the driver's side.

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Find the rubber hose part of the top cooler line as shown in Figure 12 and cut it. Some trans fluid will leak.

Secure the hoses you ran from the cooler with wire ties so they are secure and away from harm. Cut the hose from the cooler so they have enough slack in them to hook up to the hose that was just cut per Figure 13. Attach the hose from the bottom of the cooler to the tube coming from the front of the Jeep (Number 1 in Figure 13). Attach the other hose from the cooler to the tube coming from the transmission (2 in Figure 13). Install clamps securely.

Step 5 – Check for leaks

Start your Jeep and let it get warm. Check for leaks at any point you spliced hose in. If there is a leak, snug the clamp up until it stops.

Step 6 – Add transmission fluid

Since some fluid was lost and the new cooler will need some, top off the transmission fluid.

Step 7 – Replace grille

Replace the grille in the reverse that you took it off. Be sure to plug the turn signals back in.

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