Differential Cover Gasket

Replace the differential cover gasket on a 2009 Aston Martin DB9, including draining and refilling the rear differential with new gear oil.

Warnings

Tools required

Parts

• Differential cover gasket × 1 — Use OEM specification
• Differential drain plug washer (if equipped) × 1 — Use OEM specification

Fluids

• 75W-140 synthetic gear oil — 1.8 qt

Preparation

1. Park the vehicle on a level surface and engage the parking brake.
2. Place wheel chocks in front of the front wheels.
3. Raise the rear of the vehicle using a lift or jack and support securely on jack stands rated for the vehicle weight.
4. Verify the vehicle is stable before working underneath.
5. Locate the rear differential assembly between the rear wheels, mounted to the rear subframe.
6. Inspect the differential cover for existing leaks or damage to assess the job scope.
7. Position the drain pan beneath the differential cover in preparation for fluid drainage.

Procedure

1. 1

   Remove differential cover fasteners
   WARNING: Before proceeding, confirm against Aston Martin DB9 workshop documentation that a serviceable bolt-on differential cover exists. The DB9's differential is integrated into the rear transaxle and may not have a conventional removable cover. If verified, locate the cover fasteners and confirm the exact count, Torx size, and loosening sequence against factory documentation before loosening anything.upported. Note: The cover is secured with a number of perimeter bolts that must be confirmed against Aston Martin DB9 workshop documentation.
2. 2

   Drain differential fluid
   Ensure the drain pan is positioned directly below the differential cover. Carefully remove one of the remaining top bolts while supporting the cover with your hand. Remove the final bolt and gently pry the cover away from the differential housing using a plastic scraper if needed. Allow the cover to tilt downward and let all gear oil drain completely into the pan. This will take several minutes. Set the cover aside on a clean surface.
3. 3

   Inspect differential interior
   With the cover removed, use a flashlight to inspect the interior of the differential housing for metal shavings, damaged gears, or excessive wear. A small amount of fine metallic residue on the magnetic drain plug (if equipped) is normal. Look for any signs of bearing failure or gear damage that would require further service. Note any abnormalities before proceeding.
4. 4

   Clean differential housing mating surface
   Using a plastic or brass gasket scraper, carefully remove all old gasket material from the differential housing mating surface. Work methodically around the entire sealing surface, taking care not to gouge or scratch the aluminum housing. Remove any remaining residue with brake cleaner and a clean shop rag. The mating surface must be completely clean and free of any old gasket material, oil, or debris for proper sealing.
5. 5

   Clean differential cover
   Thoroughly clean the differential cover, removing all old gasket material from the mating surface using the gasket scraper. Clean both the inside and outside of the cover with brake cleaner. If equipped with a magnetic drain plug on the inside of the cover, clean all metallic debris from the magnet. Inspect the cover for cracks or warping; replace if damaged. Dry the cover completely before proceeding.
6. 6

   Install new gasket on differential cover
   Position the new differential cover gasket onto the differential cover. The gasket should fit precisely around all bolt holes and the perimeter of the cover. Some gaskets are self-adhesive; if not, a thin film of gear oil on the cover surface will help hold the gasket in place during installation. Ensure the gasket is properly seated and all bolt holes align correctly.
7. 7

   Reinstall differential cover
   Carefully position the differential cover with the new gasket against the differential housing, ensuring the gasket remains properly aligned. Start all perimeter bolts by hand, threading them in a few turns to hold the cover in position. Do not tighten any bolts until all are started to ensure even alignment and prevent gasket distortion.
   Torque spec

   Differential Cover Bolts35 Nm (26 lb-ft)
8. 8

   Torque differential cover bolts
   Using a torque wrench, tighten the differential cover bolts to the factory-specified torque in a crisscross pattern (verify exact value against Aston Martin documentation). Start with one bolt, then move to the bolt opposite or diagonal to it, working around the cover systematically. This ensures even pressure distribution and prevents gasket distortion or leaks. After the initial torque sequence, make a second pass in the same pattern to verify all bolts are properly torqued. Note: Using a torque wrench, tighten the differential cover bolts to the value specified in the Aston Martin DB9 workshop manual, in a crisscross pattern.
   Torque spec

   Differential Cover Bolts35 Nm (26 lb-ft)
9. 9

   Refill differential with gear oil
   Locate the final drive/transaxle fill-level plug per Aston Martin DB9 workshop documentation (location and fastener type vary on the integrated transaxle). Remove the plug using the factory-specified tool. Using a fluid pump or funnel with extension hose, add the Aston Martin-specified final drive gear oil through the fill port (verify exact grade and specification against factory documentation). Fill until oil begins to seep from the fill hole, indicating the correct level. Verify the exact fill capacity against Aston Martin documentation. The fill hole serves as the level indicator. Reinstall and tighten the fill plug securely. Note: Using a fluid pump or funnel with extension hose, add the Aston Martin-approved gear oil of the specification listed in the DB9 workshop manual through the fill port (verify grade before filling). Note: Fill until oil begins to seep from the fill hole, indicating the correct level. Confirm the exact fluid capacity against Aston Martin DB9 workshop documentation.
10. 10

    Inspect for leaks
    Wipe down the entire differential cover and surrounding area with a clean rag to remove any spilled gear oil. Inspect the cover gasket sealing surface carefully for any signs of leakage. Check that all bolts are properly torqued and the gasket is seating evenly around the entire perimeter. Address any visible leaks before lowering the vehicle.
11. 11

    Lower vehicle and perform final checks
    Remove the drain pan and any tools from beneath the vehicle. Carefully lower the vehicle from the jack stands or lift. Remove wheel chocks. With the vehicle on the ground, start the engine and allow it to reach operating temperature. If equipped with a limited-slip differential, follow the Aston Martin DB9-specified break-in or circulation procedure (if any) after fluid service; verify requirements against factory documentation before driving. Re-inspect the differential cover for leaks after the test drive.

Reassembly

1. Torque all differential cover bolts in a crisscross pattern as specified to ensure even gasket compression.
2. Verify the differential is filled to the correct level using the fill plug hole as the indicator.
3. Dispose of used gear oil properly at a recycling facility; do not pour down drains or onto the ground.

Verification

• Inspect the differential cover gasket sealing surface for any signs of gear oil leakage immediately after installation and again after a test drive.
• Verify the differential fill level by confirming oil reaches the bottom of the fill plug hole when the vehicle is level.
• Check that all cover bolts are torqued to specification and none show signs of looseness.
• Listen for any unusual noises from the differential during the test drive that might indicate improper assembly or low fluid level.
• After 50-100 miles of driving, re-inspect the differential cover for any delayed seepage or leaks and retorque bolts if necessary.

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