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Audi A6 C6: How to Change Fluid in Quattro System (Front and Rear Differentials)

Is your A6 Quattro due for a front and rear differential oil change? Save yourself some hard earned money by doing it yourself and follow our step-by-step guide.

By Brett Foote - June 10, 2016

This article applies to the Audi A6 C6 (2005-2011).

Though it needn't be changed nearly as often as your engine oil, ignoring differential oil can be a costly mistake. If you enjoy your Audi A6, and appreciate the Quattro all wheel drive system, you'll change the fluid periodically to insure a long life. Like any other part that contains moving pieces in your vehicle, proper lubrication is vital to extending the life of these expensive bits. Luckily, changing out the front and rear differential oil on your Quattro is a pretty simple and straightforward job that you can do yourself at home. Keep reading and we'll walk you through the process.

Audi A6 C6: How to Change Fluid in Quattro System (Front and Rear Differentials)

Materials Needed

  • Fluid extraction tool/pump
  • Floor jack and jack stands
  • 10mm Allen wrench or socket
  • 3-4 quarts of GL-5 gear/diff oil
  • Drain pan
  • Torque wrench

Step 1 – Change front differential fluid

Jack up the car and place it on jack stands. Remove the passenger side wheel and tire. The plug for the front differential is located on the passenger side of the differential (Figure 3), right by the CV joint flange. Since the front differential in the A6 C6 Quattro doesn't have a drain plug, you must excavate the 1.1 liter of old oil using a fluid pump of some sort.

  • Remove the drain/fill plug using a 10mm Allen wrench or socket (preferred).
  • Insert the hose for your pump and pump all the old oil out.
  • Store the old oil in a catch pan, to later dispose of.
  • Insert the end of the pump in fresh oil.
  • Pump approximately 1.1 liters into the differential.
  • When fluid starts to dribble out of the hole, the differential is full.
  • Replace the fill plug and torque to 26 lb-ft.
  • You can get a pump like this at most auto parts stores
    Figure 1. You can get a pump like this at most auto parts stores.
  • With the transmission out it is easy to see the fill plug
    Figure 2. With the transmission out it is easy to see the fill plug.
  • The fill plug for the front differential, located on the passenger side
    Figure 3. The fill plug for the front differential, located on the passenger side.

Step 2 – Change rear differential fluid

The rear differential has standard drain and fill plugs. Remove the fill plug first, located on the passenger side just behind the rear CV joint flange, to ensure you can refill the differential after you drain it.

  • Remove the fill plug using a 10mm Allen wrench or socket.
  • Place a drain pan underneath the drain plug.
  • Remove the drain plug and allow all of the fluid to drain.
  • Reinstall the drain plug and torque it to 26 lb-ft.
  • Using the pump, fill the rear differential with about 1.75 liters of fluid.
  • Slowly add fluid until you see fluid drip out of the hole.
  • Reinstall the fill plug and torque it to 26 lb-ft.
  • Figure 4. The fill plug for the rear differential, located behind the rear CV joint.
  • Figure 5. The drain plug for the rear differential.

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