Replace the front differential axle seal on a 2016-2024 Hyundai Tucson 2.5L AWD to repair differential fluid leaks at the axle shaft interface.

Warnings

Tools required

Parts

• Front differential axle seal × 1 — Use OEM specification
• Differential fill plug gasket/washer × 1 — Use OEM specification
• New axle nut (if staked type) × 1 — Use OEM specification

Fluids

• 75W-90 GL-5 Gear Oil — 1.5 qt

Preparation

1. Park vehicle on level surface and engage parking brake
2. Loosen the front wheel lug nuts on the side being serviced while vehicle is on ground
3. Raise and support vehicle securely on jack stands at manufacturer-recommended lift points
4. Remove the front wheel on the side being serviced
5. Place drain pan under front differential

Procedure

1. 1

   Remove axle nut
   With vehicle still on jack stands and wheel removed, have an assistant apply brakes or use a pry bar to prevent hub rotation. Use a breaker bar and appropriate socket (typically 32mm) to remove the front axle nut. If nut is staked, you may need to use a chisel to unstake first. Discard the axle nut if it is the staked type.
   Torque spec

   Axle Nut250 Nm (184 lb-ft)
2. 2

   Disconnect CV axle from differential
   Locate the inner CV joint where it connects to the front differential output flange. Remove the CV joint-to-differential bolts (typically 6 bolts). Support the axle shaft to prevent it from dropping and damaging the outer CV boot. Pull the inner CV joint away from the differential and secure the axle to the suspension with wire or a bungee cord to keep it out of the way.
   Torque spec

   CV Bolts61 Nm (45 lb-ft)
3. 3

   Drain differential fluid
   Position drain pan directly under the front differential. Remove the differential drain plug (if equipped) or the fill plug located on the side of the differential housing. Allow all gear oil to drain completely into the pan. If there is no drain plug, you will lose fluid when removing the axle seal, so have the drain pan positioned appropriately.
   ⚠Gear oil may drain quickly once plug is removed. Ensure drain pan is properly positioned.
4. 4

   Remove the old axle seal
   Inspect the differential housing where the axle shaft enters. The seal is seated in the housing bore. Using a seal puller, pry bar, or screwdriver, carefully pry out the old axle seal. Work around the perimeter to avoid cocking the seal. Be careful not to damage the seal bore surface in the differential housing as this will cause the new seal to leak.
   ⚠Do not gouge or scratch the seal bore in the differential housing. Damage to this surface will prevent proper sealing.
5. 5

   Clean and inspect seal bore
   Thoroughly clean the seal bore in the differential housing using a shop towel and wire brush. Remove all old seal residue, dirt, and debris. Inspect the bore for any damage, scoring, or corrosion. Also inspect the axle shaft sealing surface for grooves or damage that could compromise the new seal. Minor imperfections can be smoothed with fine sandpaper.
   ℹ️If the axle shaft sealing surface is deeply grooved or damaged, the axle shaft should be replaced to prevent premature seal failure.
6. 6

   Install new axle seal
   Lightly coat the outer diameter of the new seal and the seal bore with clean gear oil. Position the new seal squarely into the bore with the seal lip facing inward toward the differential. Using a seal driver or large socket that matches the outer diameter of the seal (not the inner diameter), carefully tap the seal into place. Drive the seal in evenly until it is fully seated and flush with the housing surface. Verify proper seating by checking that the seal is even all the way around.
   ⚠Use a driver that contacts only the outer metal edge of the seal. Hitting the inner portion can damage the seal lip and cause immediate failure.
7. 7

   Reinstall CV axle to differential
   Lightly coat the axle shaft sealing surface with clean gear oil. Carefully guide the inner CV joint back onto the differential output flange, ensuring the splines align properly. Install the CV joint-to-differential bolts and tighten them evenly in a cross pattern to the specified torque of 61 Nm (45 lb-ft).
   Torque spec

   CV Bolts61 Nm (45 lb-ft)
8. 8

   Reinstall axle nut
   Ensure the axle shaft is fully seated in the hub. Install a new axle nut (if staked type) onto the axle shaft threads. Using a torque wrench, tighten the axle nut to 250 Nm (184 lb-ft) while preventing hub rotation. If the nut is the staked type, use a punch and hammer to stake the nut collar into the axle shaft groove. If it uses a cotter pin, install a new cotter pin and bend the ends to secure.
   Torque spec

   Axle Nut250 Nm (184 lb-ft)
9. 9

   Refill front differential
   Locate the fill plug on the side of the front differential housing. Using a fluid pump or funnel with hose, add 75W-90 GL-5 gear oil until it begins to run out of the fill hole (approximately 1.5 quarts). Install a new fill plug gasket/washer and reinstall the fill plug. Clean any spilled fluid from the differential housing.
   ℹ️The differential is filled to the correct level when fluid reaches the bottom of the fill plug hole. Do not overfill.
10. 10

    Reinstall wheel and lower vehicle
    Reinstall the front wheel, threading lug nuts by hand first. Lower the vehicle until the tire just contacts the ground but vehicle weight is still on jack stands. Torque the lug nuts to 140 Nm (103 lb-ft) in a star pattern. Fully lower the vehicle and remove jack stands.
    Torque spec

    Wheel Lug Nuts140 Nm (103 lb-ft)

Reassembly

1. Ensure all fasteners are torqued to specification before test driving
2. Double-check that the axle nut is properly staked or cotter pin is installed
3. Verify no tools or rags were left in the work area

Verification

• Start the engine and turn the steering wheel lock-to-lock to circulate fluid through the front differential
• Check for leaks around the new axle seal while the engine is running
• Test drive the vehicle and verify normal operation with no unusual noises from the front differential or CV joints
• After test drive, recheck the differential fluid level and top off if necessary
• Inspect the seal area again after 50-100 miles of driving to confirm no leaks have developed

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