Axle Seal - Rear

This procedure covers the replacement of the rear axle seal on a 2007 Ram 3500 with 5.9L Cummins diesel and 4WD, preventing differential fluid leaks at the axle shaft.

Warnings

Tools required

Parts

• Rear axle shaft seal × 1 — Use OEM specification for AAM 10.5 or 11.5 rear axle
• Differential cover gasket × 1 — Use OEM specification for AAM 10.5 or 11.5 rear axle
• Differential cover bolt set × 1 — Use if existing bolts are damaged

Fluids

• 75W-90 synthetic gear oil — 5.5 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 securely on jack stands rated for vehicle weight
5. Remove rear wheels completely
6. Place drain pan under differential cover
7. Identify which side has the leaking seal by inspecting for fluid traces on backing plate and tire

Procedure

1. 1

   Drain differential fluid
   Remove all differential cover bolts in a criss-cross pattern, leaving the top two bolts loose. Carefully break the seal of the cover and allow fluid to drain into the pan. Once mostly drained, remove the final two bolts and remove the cover completely. Inspect drained fluid for metal particles or unusual debris which may indicate internal damage.
2. 2

   Clean differential cover mating surfaces
   Use a plastic scraper to remove old gasket material from both the differential housing and the cover. Clean surfaces thoroughly with brake cleaner and shop rags. Ensure no gasket material falls into the differential housing.
3. 3

   Remove axle shaft retainer nuts
   This axle uses a full-floating design. Remove the eight axle flange bolts (or nuts) securing the axle shaft flange to the wheel hub on the affected side. There is no bearing retainer attached to the backing plate on this design.
4. 4

   Extract axle shaft
   Grip the axle shaft flange and pull the shaft straight out of the axle tube by hand. On this full-floating design the shaft slides out freely and the wheel bearing remains in the hub. Support the shaft as it comes free to prevent it from falling. A few taps with a soft mallet on the flange may help free a stubborn shaft.
   ⚠Do not damage the brake backing plate or ABS sensor wire during axle removal.
5. 5

   Remove old axle seal
   On this full-floating axle, identify the correct leaking seal (typically the inner spindle/hub seal or the axle tube seal). Using the appropriate seal puller, carefully extract the old seal without damaging the sealing surface. If the seal is difficult to remove, use a pick to create a starting point for the puller. Inspect the bore for scoring or damage.
6. 6

   Clean and inspect axle tube
   Clean the axle tube seal bore thoroughly with brake cleaner and a shop rag. Use a wire brush if necessary to remove any rust or debris. Inspect the seal surface for grooves or damage that could cause the new seal to leak. Clean the axle shaft sealing surface where it contacts the seal, removing any rust or pitting.
7. 7

   Install new axle seal
   Lightly coat the outer diameter of the new seal with gear oil. Position the seal squarely in the axle tube bore with the seal lip facing inward toward the differential. Using a seal driver or appropriately sized socket that contacts only the outer edge of the seal, drive the seal into the bore until it is fully seated and flush with the axle tube end. Ensure the seal is not cocked or damaged during installation.
   ⚠Do not strike the center of the seal as this will damage the sealing element. Only contact the outer metal edge.
8. 8

   Inspect and prepare axle shaft
   Inspect the axle shaft sealing surface for grooves, rust, or damage. Use fine emery cloth to smooth any minor imperfections. The seal rides on this surface, so it must be smooth. Coat the axle shaft seal journal with clean gear oil before installation.
9. 9

   Reinstall axle shaft
   Carefully guide the axle shaft into the axle tube, ensuring it does not damage the new seal. Align the splines with the differential side gear and push the shaft in until the bearing retainer contacts the backing plate. You may need to rotate the shaft slightly to engage the splines. The shaft should slide in smoothly once properly aligned.
10. 10

    Secure axle shaft retainer
    Install the axle flange bolts and tighten in a criss-cross pattern. Torque to manufacturer specification for the AAM 10.5/11.5 axle (verify exact spec in the service manual). Ensure the flange seats flush against the hub.
11. 11

    Install differential cover
    Position the new gasket on the differential cover or housing as designed. Some gaskets use RTV sealant instead of a paper gasket - follow the gasket manufacturer instructions. Align the cover onto the housing and install all bolts hand-tight. Tighten bolts in a criss-cross pattern to ensure even gasket compression. Typical specification is 30-35 ft-lbs, but tighten gradually and evenly.
12. 12

    Refill differential with gear oil
    Remove the differential fill plug (located on the differential cover or rear face of the housing). Using a fluid pump or squeeze bottle, add 75W-90 synthetic gear oil until fluid begins to drip from the fill hole. If the axle is equipped with a limited-slip differential, add the specified friction modifier. The differential is full when fluid reaches the bottom of the fill plug hole (approximately 3-3.5 quarts depending on AAM 10.5 or 11.5 axle). Install and tighten the fill plug securely.
13. 13

    Reinstall wheel and lower vehicle
    Reinstall the rear wheel and thread lug nuts by hand. Lower the vehicle until the tire just contacts the ground. Torque lug nuts to 135 ft-lbs in a star pattern. Fully lower the vehicle and remove jack stands.

Reassembly

1. Ensure all fasteners are torqued to specification
2. Verify differential is filled to proper level
3. Double-check that no tools or parts were left under the vehicle

Verification

• Wipe the axle tube and backing plate area clean with a shop rag
• Test drive the vehicle for 10-15 miles, including some turning to distribute the gear oil
• Re-inspect the seal area for any signs of leakage after test drive
• Check differential fluid level again after test drive and top off if necessary
• Monitor the seal area over the next few days for any delayed leakage

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