Axle Seal - Rear

Replace the rear axle seal(s) to stop differential fluid leaks at the axle shaft(s) on the AMC 20 rear axle assembly.

Warnings

Tools required

Parts

• Rear axle shaft seal (driver side) × 1 — AMC 20 axle seal, verify flange or tapered shaft type
• Rear axle shaft seal (passenger side) × 1 — AMC 20 axle seal, verify flange or tapered shaft type
• Differential cover gasket × 1 — AMC 20 rear differential cover gasket or RTV gasket maker
• Axle shaft retainer nuts × 8 — Use OEM specification if reusing is not possible

Fluids

• GL-5 85W-90 or 80W-90 gear oil — 3 qt

Preparation

1. Park vehicle on level surface and engage parking brake
2. Chock front wheels securely
3. Loosen rear wheel lug nuts while vehicle is on ground
4. Raise rear of vehicle and support on jack stands at frame or rear axle housing (depending on which side being serviced)
5. Remove rear wheels
6. Place drain pan under differential cover

Procedure

1. 1

   Drain differential fluid
   Remove all bolts from the differential cover and carefully break the cover seal. Allow gear oil to drain completely into the drain pan. Once drained, remove the differential cover completely and set aside. Clean the gasket surfaces on both the housing and cover with a wire brush and shop rags.
2. 2

   Remove brake drum
   Remove the brake drum retaining clips if present. Pull the brake drum off the axle shaft studs. If the drum is stuck, use a rubber mallet to tap around the outer edge to break it free. Ensure parking brake is fully released.
3. 3

   Remove axle shaft retaining nuts
   Using a 3/4 inch socket, remove the four nuts securing the axle shaft flange to the brake backing plate. These nuts also hold the backing plate to the axle housing. Mark the orientation of the backing plate relative to the axle housing for reassembly.
4. 4

   Extract axle shaft
   Attach a slide hammer with axle puller adapter to the axle shaft flange studs. Use the slide hammer to pull the axle shaft out of the housing. The shaft should come out with the bearing and seal remaining in the housing. If resistance is met, verify all retaining nuts are removed and continue with firm, steady pulls on the slide hammer.
5. 5

   Remove old axle seal
   Using a seal puller or pry bar, carefully remove the old seal from the axle housing bore. Work around the seal circumference to avoid damaging the housing bore. Inspect the seal bore for any burrs, scratches, or damage that could compromise the new seal.
6. 6

   Inspect axle shaft and bearing
   Examine the axle shaft seal surface for grooves, pitting, or damage. Check the axle bearing for roughness, noise, or excessive play. If the bearing or shaft shows wear, replacement is recommended before installing new seals. Clean the axle shaft seal surface with a shop rag.
7. 7

   Install new axle seal
   Lightly coat the outer diameter of the new seal with gear oil. Position the seal squarely in the housing bore with the seal lip facing inward toward the differential. Using a seal driver or appropriately sized large socket, carefully drive the seal into the bore until it is fully seated and flush with the housing face. Ensure the seal goes in straight to prevent cocking or damage.
8. 8

   Reinstall axle shaft
   Coat the axle shaft seal surface and bearing journal lightly with gear oil. Carefully guide the axle shaft into the housing, ensuring it engages the differential side gear splines. Push the shaft in fully until the bearing seats in the housing bore. Take care not to damage the new seal lip during insertion.
9. 9

   Secure axle shaft and backing plate
   Align the brake backing plate with the marks made during disassembly. Install the four retaining nuts onto the axle flange studs, threading them through the backing plate and into the axle housing. Tighten the nuts in a criss-cross pattern progressively. Final torque should be 40-50 ft-lbs, though verify with service manual if available.
10. 10

    Reinstall brake drum
    Slide the brake drum onto the axle shaft studs, ensuring it seats properly against the hub face. Install drum retaining clips if originally equipped. Verify the drum rotates freely without binding on brake shoes.
11. 11

    Install differential cover
    Clean the differential cover and housing gasket surfaces thoroughly. Install a new gasket or apply a 1/8 inch bead of RTV silicone gasket maker to the cover. Position the cover on the housing and install all bolts finger-tight. Tighten bolts in a criss-cross pattern to 20-25 ft-lbs to ensure even gasket compression and prevent leaks.
12. 12

    Refill differential with gear oil
    Locate the differential fill plug on the front of the housing (passenger side). Remove the fill plug. Add GL-5 85W-90 or 80W-90 gear oil through the fill hole until oil begins to run out of the hole. The AMC 20 rear axle capacity is approximately 2.5 to 3 quarts. Reinstall and tighten the fill plug.

Reassembly

1. Repeat steps 2-12 for the opposite side if replacing both seals
2. Reinstall rear wheels and tighten lug nuts in a star pattern
3. Lower vehicle to ground and torque lug nuts to 75-80 ft-lbs
4. Allow RTV gasket maker to cure per manufacturer instructions (typically 1 hour) before test driving if used

Verification

• Check for gear oil leaks around the differential cover and axle shaft seals after reassembly
• Test drive the vehicle and verify no abnormal noises from the rear axle
• Re-check differential fluid level after test drive and top off if necessary
• Inspect axle seal areas again after 50-100 miles of driving to confirm no leakage

More procedures for this vehicle