Last year, 88,000 JKs were recalled for potential automatic transmission overheating. You might think that the fix was to install a transmission cooler or some other mechanical upgrade to better control the transmission temperature. Nope. When you roll into your dealership for the recall, they install a trans temp idiot light, and they instruct you to pull over and park your Jeep if that light ever comes on. Right.
For right around $50, we came up with a solution that we feel a whole lot better about: adding a Flex-a-lite transmission cooler. Part number 4118 fits nicely behind the grille, and with a GVWR rating of 18,000 pounds, it’s more than triple the cooling capacity that a JK should ever need. This cooler is made in the U.S. and features Turbulators—twisted inserts that increase heat transfer from the ATF to the copper tubes and cooling fins.
We took some rough measurements...
We took some rough measurements of the space in front of the grille and found that a Flex-a-lite 4118 would fit well. This is a six-pass cooler that measures 7½x15 inches overall. You can mount the cooler vertically or horizontally, but don’t mount it with fittings facing down. In a JK, the most natural way to mount it is with the fittings facing the driver-side headlight.
The Flex-a-lite cooler included push-tie mounts, barbed fittings, hose clamps, and a length of rubber hose. To mount it in a JK the way that we show here, you’ll also need two 3⁄8-inch fittings with barbed ends on both sides, two extra hose clamps, a couple of more feet of 3⁄8-inch rubber tranny cooler hose, and about three feet of steel strapping. Fitting the cooler to our Jeep was a snap, taking just over two hours, and that was with custom mounting work for a super clean installation. Even if your JK wasn’t affected by the recall, this is an easy and inexpensive upgrade that can extend the life and performance of your automatic transmission.
Let your Jeep cool down before...
Let your Jeep cool down before doing this install. Removing the grille on a JK is very easy. They have six two-piece plastic fasteners across the top. Use a small screwdriver to pry out the center, and then gently remove the remaining part with the screwdriver or by hand. Lean the top of the grille away from the vehicle and remove the marker lights by twisting the plug assemblies 90 degrees. Along the bottom of the grille are push clips; wiggle the grille side-to-side and pull these free from the body.
We decided not to mount the...
We decided not to mount the cooler directly to the radiator and A/C condenser. Instead, we purchased 1x3⁄16-inch steel strap to create two rigid brackets. We cut it to length and bent the ends to mount between the upper and lower sections of the core support. Here we are marking the point for the lower bend. We bent the strap with a vice and a large hammer, and we used a bench grinder to round the edges.
We used the plastic bolts...
We used the plastic bolts and rubber cushions that came with the cooler to attach it to our brackets. We determined the exact placement of the brackets so they would not interfere with the wiring loom across the top of the core support. Flex-a-lite also offers GatorClips which clamp to the exposed bends of the copper tubes and then can be bolted to our brackets to avoid using the plastic bolts through the cooler fins.
We used dual barbed-end fittings...
We used dual barbed-end fittings to splice into the factory trans cooler lines. To save yourself some work once you’re under the vehicle, mock up the lines to determine the length and best routing. Make sure the hoses will not rub against sharp edges. Cut the hoses and clamp the fittings to the ends. We needed about two additional feet of 3⁄8-inch rubber tranny cooler hose for our install.
Put a container under the...
Put a container under the vehicle to catch the very small amount of trans fluid that will drain when you cut the line. Splice into the line that is on top and slightly rearward, and make sure that the fluid coming from the trans goes into the top of the new Flex-a-lite cooler.
In this photo you can see...
In this photo you can see the exact position we chose for the cooler and the brackets on the core support. We drilled four holes and used sheetmetal bolts to attach our custom brackets. Having the new trans cooler about 1½ inches off of the A/C condenser improves airflow compared to having it mounted directly to it. Check the trans-fluid level after the installation. Double-check all six hose clamps and the routing of the rubber lines, then reinstall the grille.