Transmission Oil Cooler

Replace the transmission oil cooler that is integrated into the radiator tank or mounted externally, requiring radiator or cooler line disconnection and fluid refilling.

Warnings

Tools required

Parts

• Transmission oil cooler assembly × 1 — Use OEM or equivalent for 47RE/48RE transmission
• Transmission cooler line O-rings or seals × 1 — Kit typically includes multiple sizes
• Transmission cooler lines (if damaged) × 1 — Use OEM specification
• Hose clamps (various sizes) × 4 — Worm-drive style 1.25-2 inch
• Coolant (if radiator-mounted cooler) × 1 — 50/50 premix green conventional or HOAT
• Transmission filter kit × 1 — Recommended during oil cooler service
• Transmission pan gasket or RTV sealant × 1 — Use OEM specification
• Shop towels × 1 — For cleanup

Fluids

• Mopar ATF+4 — 14 qt
• Ethylene glycol 50/50 coolant — 2 qt

Preparation

1. Park vehicle on level ground and apply parking brake
2. Place wheel chocks behind rear wheels
3. Allow engine and transmission to cool completely (minimum 2 hours)
4. Disconnect negative battery cable
5. Raise front of vehicle and support on jack stands at frame rails
6. Remove front skid plate if equipped
7. Place large drain pan under transmission pan
8. Identify transmission cooler configuration (radiator-mounted or external auxiliary cooler)

Procedure

1. 1

   Drain transmission fluid
   Remove transmission pan drain plug if equipped, or loosen all pan bolts and carefully pry one corner down to drain fluid. Allow fluid to drain completely into drain pan. Inspect drained fluid for coolant contamination (milky pink appearance indicates failed cooler). If no drain plug, remove all pan bolts and lower pan completely.
   Torque spec

   Drain Plug34 Nm (25 lb-ft)
2. 2

   Remove transmission pan and filter
   Remove remaining transmission pan bolts in criss-cross pattern. Lower pan and gasket. Remove transmission filter by pulling straight down - expect residual fluid spillage. Clean pan thoroughly and inspect for debris. Check magnet for excessive metal particles indicating internal damage.
   ℹ️Replacing filter during cooler service prevents contaminated fluid from circulating through new cooler.
   Torque spec

   Transmission Pan Bolts12 Nm (9 lb-ft)
3. 3

   Drain engine coolant (if radiator-mounted cooler)
   If cooler is integrated into radiator, place drain pan under radiator and open radiator petcock or remove lower radiator hose. Drain approximately 2 gallons of coolant. If external cooler only, skip this step.
   Torque spec

   Drain Petcock7 Nm (5 lb-ft)
4. 4

   Access and identify transmission cooler lines
   Locate transmission cooler lines at radiator or external cooler (typically on passenger side of radiator or mounted in front of radiator). Identify supply line (from transmission) and return line (to transmission). Clean area around fittings thoroughly. Note routing and orientation of lines for reinstallation.
   ℹ️Supply line typically connects to lower radiator tank connection, return line to upper connection.
5. 5

   Disconnect transmission cooler lines
   Using line wrenches to prevent rounding, carefully loosen cooler line fittings at radiator or external cooler. If quick-disconnect fittings are used, depress release tabs with proper tool while pulling line away. Cap open lines immediately to prevent contamination. Expect additional fluid drainage. Do not use standard open-end wrenches on transmission line fittings as this will round off the fittings.
   ⚠Do not use standard open-end wrenches on transmission line fittings as this will round off the soft brass/aluminum fittings.
6. 6

   Remove old transmission cooler
   If radiator-mounted cooler: cooler is part of radiator assembly and cannot be serviced separately - radiator replacement required. If external auxiliary cooler: remove mounting bolts securing cooler to frame or radiator support. Disconnect any remaining lines and remove cooler assembly. Inspect mounting location for damage or corrosion.
7. 7

   Inspect transmission cooler lines
   Inspect full length of transmission cooler lines for cracks, kinks, rust, or damage. Check rubber hose sections for softness or cracking. Replace lines if any damage is found. Inspect line mounting clips and brackets for security.
   ℹ️Failed cooler lines are a common cause of transmission fluid loss and overheat on these vehicles.
8. 8

   Install new transmission cooler
   Position new external cooler in mounting location with fittings oriented correctly. Install mounting bolts finger-tight, then torque to specification. Ensure cooler has adequate clearance from radiator and other components. If replacing radiator for integrated cooler, follow radiator replacement procedure.
9. 9

   Connect transmission cooler lines
   Install new O-rings or seals on cooler line fittings - lubricate with clean ATF+4. Connect lines to cooler fittings, ensuring correct routing without kinks or sharp bends. Thread fittings carefully by hand to prevent cross-threading. Tighten fittings with line wrenches until snug - do not overtighten fittings. Overtightening transmission line fittings will crack the cooler or strip threads. Tighten fittings to the manufacturer-specified torque value; consult the service manual for the exact spec. If quick-disconnect style, push firmly until click is heard and verified by pull test.
   ⚠Overtightening transmission line fittings will crack the cooler or strip threads. Snug plus 1/4 turn is sufficient for most fittings.
   Torque spec

   Hose Clamps3 Nm (2 lb-ft)
10. 10

    Install new transmission filter and pan
    Install new transmission filter by pushing straight up into valve body until fully seated. Clean pan and transmission mating surfaces thoroughly. Install new pan gasket or apply RTV sealant per manufacturer instructions. Position pan and install bolts finger-tight. Torque pan bolts in criss-cross pattern to specification.
    ℹ️If using RTV sealant, allow proper cure time before filling with fluid per sealant manufacturer instructions.
    Torque spec

    Transmission Pan Bolts12 Nm (9 lb-ft)
11. 11

    Refill engine coolant (if applicable)
    If coolant was drained, close radiator petcock or reconnect lower hose with new clamp. Refill cooling system with appropriate coolant through radiator cap or overflow tank. Burp air from system by running engine with heater on high until thermostat opens and coolant level stabilizes.
    Torque spec

    Drain Petcock7 Nm (5 lb-ft)

    Hose Clamps3 Nm (2 lb-ft)
12. 12

    Refill transmission fluid
    Add approximately 6-8 quarts of Mopar ATF+4 through transmission dipstick tube using fluid pump or funnel with long tube. Install dipstick and start engine. With engine idling and parking brake applied, shift through all gear ranges, pausing 2-3 seconds in each. Return to Park and check fluid level with engine running. Add fluid as needed to bring to the COLD/AMBIENT mark on dipstick, then recheck and adjust to the HOT mark once fluid reaches operating temperature. Total system dry-fill capacity is approximately 17-19 quarts depending on transmission and cooler configuration, but initial pan-only fill is lower due to fluid retained in the torque converter and valve body; verify exact capacity against the service manual.
    ℹ️Total system capacity is 14 quarts, but initial fill is lower due to fluid retained in torque converter and valve body.
13. 13

    Check for leaks and perform initial test
    With engine running in Park, carefully inspect all cooler line connections, pan gasket, and drain plug for leaks. Check coolant level and look for signs of coolant in transmission fluid or vice versa. Allow transmission to reach operating temperature (15-20 minutes of idling). Recheck fluid level and add to HOT mark as needed. Test drive vehicle through all gears.
    ⚠Do not operate vehicle if any leaks are detected. Transmission damage will occur rapidly with low fluid level.

Reassembly

1. Reinstall front skid plate if equipped
2. Lower vehicle from jack stands
3. Reconnect negative battery cable
4. Double-check all cooler line connections for tightness
5. Verify transmission fluid is at proper level on HOT mark after test drive
6. Clean any spilled fluids from frame and components

Verification

• Check transmission fluid level with engine running at operating temperature - should be at HOT mark on dipstick
• Verify no fluid leaks from cooler connections, pan gasket, or drain plug after test drive
• Confirm transmission shifts smoothly through all gears without slipping or delayed engagement
• Check coolant level is stable with no signs of transmission fluid contamination (reddish tint in coolant)
• Verify transmission fluid is clean red color with no milky appearance indicating coolant contamination
• Monitor transmission temperature during operation - should remain below 200°F under normal driving conditions
• Recheck fluid level after 50-100 miles of driving and top off if necessary

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