Differential Fluid Change - Rear

Drain and refill the rear differential with fresh 75W-140 synthetic gear oil to maintain proper lubrication and extend differential lifespan.

Warnings

Tools required

Parts

• Drain plug crush washer × 1 — Use OEM specification
• Fill plug crush washer × 1 — Use OEM specification

Fluids

• 75W-140 synthetic gear oil — 1.8 qt

Preparation

1. Park vehicle on level surface and engage parking brake
2. Allow differential to cool if vehicle was recently driven
3. Raise vehicle on lift or secure on jack stands at all four corners
4. Verify vehicle is stable before working underneath
5. Have drain pan and fresh gear oil ready before removing drain plug

Procedure

1. 1

   Locate differential drain and fill plugs
   Position yourself beneath the rear of the vehicle. The DB9 uses a rear-mounted transaxle that integrates the final drive/differential; locate the final drive fill and drain plugs on the transaxle unit at the rear of the vehicle per Aston Martin documentation. Identify the drain plug on the lower portion of the differential housing and the fill plug on the side or upper rear face of the housing. Clean the area around both plugs with a wire brush to prevent contamination when removed. Note: Position yourself beneath the rear of the vehicle. On the DB9 the final drive/differential is part of the rear transaxle assembly. Identify the drain and fill plug locations per Aston Martin service data (verify exact positions before proceeding). Clean the area around both plugs.
2. 2

   Remove fill plug first
   Using the correct hex socket size (verify against Aston Martin factory documentation), loosen and remove the fill plug BEFORE removing the drain plug. This confirms you can refill the differential after draining. If the fill plug is seized, do not proceed with draining. Set the fill plug and old crush washer aside. Note: Hex socket for drain/fill plugs (verify exact size against Aston Martin factory documentation)
3. 3

   Drain differential fluid
   Position drain pan beneath the drain plug. Using the appropriate hex socket, slowly loosen the drain plug. Once loose, quickly remove it by hand and allow old fluid to drain completely into the pan. This will take several minutes. Inspect drained fluid for metal particles or abnormal debris, which may indicate internal wear.
4. 4

   Clean and inspect drain plug
   Once fluid has fully drained, clean the drain plug with shop rags. Inspect the plug threads and magnetic tip (if equipped) for damage or excessive metal shavings. Wipe clean the sealing surface around the drain hole on the differential housing.
5. 5

   Install drain plug with new washer
   Install a new crush washer onto the drain plug. Thread the drain plug into the housing by hand to avoid cross-threading, then tighten to the Aston Martin-specified torque for the final drive drain plug (verify against factory documentation) using a torque wrench. Do not overtighten as the aluminum housing threads are vulnerable to damage. Note: Thread the drain plug into the housing by hand to avoid cross-threading, then tighten to the Aston Martin factory-specified drain plug torque (verify exact value against factory documentation) using a torque wrench. Note: torqueRefs": [ "Differential Drain Plug" ] Note: Install a new crush washer onto the drain plug. Thread the drain plug into the housing by hand to avoid cross-threading, then tighten to the OEM-specified torque (verify in Aston Martin service data) using a torque wrench. Do not overtighten as the aluminum housing threads are vulnerable to damage.
   Torque spec

   Differential Cover Bolts35 Nm (26 lb-ft)
6. 6

   Fill differential with fresh gear oil
   Using a fluid pump or funnel with extension hose inserted into the fill hole, add the Aston Martin-specified synthetic gear oil (verify exact grade and limited-slip requirements against factory documentation) slowly. Fill until oil begins to seep from the fill hole, indicating proper level. Verify the exact final-drive fluid capacity against Aston Martin service documentation before filling, as the DB9 rear transaxle capacity differs from a conventional differential. Allow a moment for oil to settle and top off if needed until oil is at the bottom edge of the fill hole threads. Note: Fill to the proper level as indicated by fluid seeping from the fill hole; verify the exact fluid capacity against Aston Martin service documentation before relying on an approximate volume. Note: Using a fluid pump or funnel with extension hose inserted into the fill hole, add the Aston Martin OEM-specified final-drive/transaxle lubricant slowly (verify exact grade against factory documentation before filling). Note: Using a fluid pump or funnel with extension hose inserted into the fill hole, add the OEM-specified synthetic gear oil slowly (verify exact grade and limited-slip additive requirement in Aston Martin service data). Fill until oil begins to seep from the fill hole, indicating proper level. Add the OEM-specified fill quantity (verify exact capacity in service data). Allow a moment for oil to settle and top off if needed until oil is at the bottom edge of the fill hole threads.
7. 7

   Install fill plug with new washer
   Install a new crush washer onto the fill plug. Thread the fill plug into the housing by hand, then tighten to the Aston Martin-specified torque for the final drive fill plug (verify against factory documentation) using a torque wrench. Wipe away any spilled gear oil from the differential housing exterior. Note: Thread the fill plug into the housing by hand, then tighten to the Aston Martin factory-specified fill plug torque (verify exact value against factory documentation) using a torque wrench. Note: torqueRefs": [ "Differential Fill Plug" ] Note: Install a new crush washer onto the fill plug. Thread the fill plug into the housing by hand, then tighten to the OEM-specified torque (verify in Aston Martin service data) using a torque wrench. Wipe away any spilled gear oil from the differential housing exterior.
   Torque spec

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

   Lower vehicle and verify
   Lower the vehicle to the ground. After lowering the vehicle, check beneath it for any leaks around the drain and fill plugs; a normal short drive can later confirm quiet operation. Check beneath the vehicle for any leaks around the drain and fill plugs.

Reassembly

1. Ensure both drain and fill plugs are torqued to specification with new crush washers installed
2. Wipe differential housing clean of any spilled gear oil to facilitate leak detection
3. Dispose of used gear oil at appropriate recycling facility

Verification

• No leaks visible around drain or fill plugs after short test drive
• Differential operates quietly without new whining or grinding noises
• Approximately 1.8 quarts of fresh 75W-140 synthetic gear oil was added
• Both plugs torqued to 35 Nm (26 lb-ft) specification

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