• 14MM Allen Socket
• Ratchet
• Two-Way Transfer Pump
• Gear Oil Hand Pump
• Drain Pan
• Full Synthetic Gear Oil

Ensure you conduct this DIY on a vehicle with a cold engine to avoid the differential oil from being hot.

Before changing the gear oil, inspect the surrounding area for any leaks. If you notice any leaks near the rear differential, it could indicate an underlying issue that needs attention.

Using a 14mm Allen socket and a ratchet, turn the fill plug counterclockwise to loosen it. On BMW differentials, the fill plug also serves as the drain plug.

Remove the drain plug from the rear differential and inspect the fill hole. If fluid was filled to a proper level, a small steady stream of gear oil will flow from the fill hole. If no gear oil flows, the differential was under-filled.

To change the gear oil, you’ll need a two-way transfer pump. We recommend this budget-friendly hand pump, which makes the job quick and hassle-free.

Insert the “IN” side of the two-way transfer pump into the differential. This end will extract the old fluid from the differential.

With the “IN” side of the hose inserted, use the hand pump to extract the old gear oil into an empty container. Continue pumping until all the old fluid is completely removed.

The rear differential on a BMW typically holds between 1 and 1.4 liters of gear oil. This specific E9X model holds 1.2 liters, so continue extracting until this amount has been fully drained from the system.

Carefully inspect the old gear oil, as its condition can reveal a lot about the health of the differential. If the fluid is dark brown or black, it indicates that it has been burned and likely hasn’t been changed in well over the recommended 50,000-mile interval.

Only approved full synthetic gear oil can be used in the differential. Using the wrong fluid can cause excessive corrosion and bad perfromance.

Non-LSD E Chassis Recommended

M3 LSD Recommended

To make this job even easier, we used an easy-fill hand pump that attaches directly to any gear oil container. This significantly reduces the chances of spills and makes the process much more convenient.

Firmly press the easy-fill nozzle from the gear oil pump into the fill plug hole with a secure push. Once installed, the adapter will stay in place, minimizing the risk of spills.

There’s a convenient cavity behind the rear driver-side wheel well that perfectly fits the gear oil bottle with the adapter. From here, simply lift the bottle and press the top against the chassis to allow the oil to flow into the differential.

With all the old gear oil drained, fill the differential with new full synthetic oil, ensuring the fluid flows smoothly through the pump.

Continue filling the differential with 1.2 liters of gear oil until a slow, steady stream begins to flow out. This indicates that the differential has reached full capacity.

We’re upgrading the differential drain plug to our aluminum version, which features a high-power magnet. This magnet helps capture harmful metal particles that could cause long-term damage to the internal gears. The factory drain plug is smooth metal and does not trap any debris, making this upgrade a valuable addition.

Tighten the differential drain/fill plug to 44 lb-ft of torque.

Clean the surrounding area with a microfiber towel. Differential fluid is highly corrosive, and any excess residue can make it harder to spot future leaks.

Test drive your BMW to ensure the differential is functioning properly, without any slippage, shuddering, or grinding sounds.

Great job changing your differential gear oil! Be sure to perform this maintenance every 40,000 to 60,000 miles to keep your differential in top condition.