Installing a Transmission Cooler on a Jeep Cherokee

Written by richard rowe
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Installing a Transmission Cooler on a Jeep Cherokee
Make your Jeep truly trail-rated by keeping it cool. (mountain jeep road image by Mike & Valerie Miller from

Oil is more than just a lubricant, it's a coolant responsible for carrying heat away from friction surfaces like bearings and valvetrain components. This function is especially critical for steeply-geared off-road vehicles that spend a lot of time going very slow with the engine revving very high. Installing an oil cooler into a Cherokee isn't particularly difficult; if you know how to change a radiator, then odds are you can install a transmission cooler. The Cherokee has gone through three major evolutions (SJ, XJ and XJ chassis) and more than a dozen engines in its 30-plus year lifespan, so installation procedures can vary greatly depending on model year and trim level.

Skill level:

Things you need

  • Oil drain pan
  • Oil cooler kit
  • New oil filter (if not included with kit)
  • Teflon tape
  • Oil
  • Basic hand tools
  • Line wrenches, full set
  • Oil filter wrench
  • Wire cutters/crimpers

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  1. 1

    Remove the oil filter, and remove the oil drain plug to drain the oil. You don't necessarily need to change the oil while installing the cooler, but you might as well. You might consider adding an oil-flushing solvent to your engine about 100 miles prior to the oil cooler install to flush sludge and junk out of your system so that it doesn't break loose and clog the cooler. Replace the drain plug and refill your crankcase with the amount of oil specified for your Jeep.

  2. 2

    Wrap the threads of your oil cooler adaptor lines with Teflon tape; wrap the Teflon tape clockwise with the fitting facing you. Install the cooler lines into the cooler adaptor plate and tighten them to your kit manufacturer's specifications. If you're using elbow-fittings, orient the fittings so that they face downward as installed in the vehicle. Coat the supplied O-ring with oil and press it into the recess in the top of the adaptor plate.

  3. 3

    Install the adaptor plate in place of the old filter. Thread the retaining nut over the threaded oil filter boss and tighten it to the manufacturer's specifications. Fill the new oil filter with oil, moisten the filter seal with oil and spin it onto the adaptor plate.

  4. 4

    Install the radiator-like oil cooler. Installation procedures will vary greatly here depending on your Jeep's model year and trim level and by which kit you decide to use. Basic kits use zip-tie-like retainers that poke through the cooler's fins and radiator fins to secure the cooler to the radiator. Higher-end kits use preformed brackets, and custom frame-rail-mount installations will require that you build custom brackets. There's no set way to mount an oil cooler; follow your manufacturer recommendations and install the cooler somewhere that it will be protected from damage and receive adequate cooling airflow.

  5. 5

    Wrap the cooler-ends of your oil cooler lines with Teflon tape and thread them onto the cooler's threaded bosses. Tighten them hand-tight, then disconnect hoses from the adaptor plate. Hold the upper cooler tube up as far as it will reach, and have an assistant go under the truck to place their thumb over the end of the lower cooler line. Insert a funnel into the upper cooler hose and pour oil into it to purge air from the system. As soon as oil begins to flow from the lower tube, have your assistant immediately connect it to the adaptor plate and tighten it down. Reinstall the upper tube onto the adaptor plate, and be prepared to catch any oil that comes out of the tube as your lower it.

  6. 6

    Start the engine and check the oil level. You'll may need to add another two to three quarts, depending on how much air remains trapped in the system. Purging the cooler as described in Step 5 isn't technically necessary, but it will greatly reduce the odds of damage or a loss of oil pressure that may require you to reprime the pump.

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