Differential Fluid Change - Rear

Drain and refill the rear differential with fresh Mercedes-Benz 75W-85 differential fluid to maintain proper lubrication and extend differential life.

Warnings

Tools required

Parts

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

Fluids

• Mercedes-Benz Diff Fluid 75W-85 — 2 qt

Preparation

1. Park vehicle on level ground and engage parking brake
2. Place wheel chocks in front of front wheels
3. Allow differential to cool for 30 minutes if recently driven
4. Raise rear of vehicle with floor jack and support securely on jack stands at designated rear jacking points
5. Remove rear wheels to improve access (optional but recommended)

Procedure

1. 1

   Locate differential drain and fill plugs
   Position yourself under the rear of the vehicle and locate the rear differential housing. Identify the drain plug on the bottom of the differential cover and the fill plug on the side of the differential housing. Clean the area around both plugs with a wire brush and shop rag to prevent contamination.
2. 2

   Remove fill plug first
   Using a 10mm hex socket, carefully loosen and remove the fill plug from the side of the differential housing. This ensures you can refill the differential after draining. If the fill plug is seized or damaged, do not proceed with draining until it can be removed.
   ⚠Always remove the fill plug before the drain plug to ensure you can refill the differential. If the fill plug is seized and you drain first, the vehicle will be immobilized.
3. 3

   Drain differential fluid
   Position the drain pan beneath the differential drain plug. Using a 10mm hex socket, loosen and remove the drain plug. Allow the fluid to drain completely for at least 10 minutes. Inspect the drained fluid for metal particles or debris which may indicate differential wear. Inspect the drain plug for a magnetic insert and clean any metal filings from it.
   ⚠Differential fluid may still be warm. Wear gloves and avoid contact with hot fluid.
4. 4

   Inspect and clean differential cover
   Once fluid has fully drained, inspect the differential cover gasket sealing surface for damage or excessive wear. Clean the drain plug threads and sealing surface with a shop rag. If equipped with a crush washer on the drain plug, replace it with a new one.
5. 5

   Reinstall drain plug
   Install the drain plug with a new washer if applicable. Thread in by hand first to ensure proper alignment, then tighten to specification. Note: The drain plug typically uses the cover bolt specification if it threads into the cover, or may have a different specification if it is a separate plug design. Hand-tighten firmly plus 1/4 turn if no specific torque is available for the drain plug itself.
6. 6

   Refill differential with fresh fluid
   Using a fluid pump or transfer syringe, insert the nozzle into the fill hole. Slowly pump in Mercedes-Benz 75W-85 differential fluid until it begins to drip out of the fill hole. The differential is properly filled when fluid reaches the bottom of the fill plug hole. Allow excess to drain back, then proceed to next step.
   ℹ️Fill slowly to allow air to escape and prevent overfilling. Approximately 2.0 quarts is required, but fill until fluid reaches the fill hole regardless of quantity used.
7. 7

   Reinstall fill plug
   Clean the fill plug threads and sealing surface. Thread the fill plug in by hand to ensure proper alignment, then tighten securely. Hand-tighten firmly plus 1/4 turn. Wipe away any spilled fluid from the differential housing.
8. 8

   Reinstall wheels and lower vehicle
   If wheels were removed, reinstall them and hand-tighten lug nuts in a star pattern. Lower the vehicle to the ground. Once the vehicle is on the ground, torque the wheel lug nuts to specification in a star pattern.
   Torque spec

   Wheel Lug Nuts140 Nm (103 lb-ft)

Reassembly

1. Dispose of used differential fluid properly at a recycling center or automotive shop
2. Check for leaks around drain and fill plugs after first drive
3. Record the service date and mileage for maintenance tracking

Verification

• Start the engine and verify no leaks from drain or fill plugs
• Test drive the vehicle for 5-10 minutes, then recheck for leaks while differential is warm
• Listen for unusual noises from the rear differential during acceleration and deceleration
• Verify smooth operation through turns without binding or chattering

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