Audi A6 C6: How to Change Manual Transmission Fluid
Manual transmission oil is typically specified for 50,000+ miles before being changed, but as with any internally lubricated component, the transmission operates at its best with fresh, clean oil. Fresh oil will keep your gears, syncros, and bearings all happily living together for many years of driving.
This article applies to the Audi A6 (2005-2011).
Although many transmissions are now factory filled with extended service lubricants, there is no denying the fact that these oil dirty up with normal vehicle usage. As oils and lubricants improve and evolve, many manufacturers are now extending their transmission oil drain intervals. In the case of Audi, they now consider their transmission oils to be "lifetime fluids" that last the life of the vehicle. What that really means is that the factory fill is good until far enough past the warranty ending that there will be no customer blowback. The transmission oil fills the voids between the transmission gears, and works to not only lubricate internal components, but to keep them cool under severe operating conditions. With use, gear oil has the potential to shear and lose its rated viscosity, plus internal parts wearing contaminates the oil with microscopic metallic particles that can affect smooth shifting operation. Changing the oil in your manual transmission will make shifting easier, combat wear, and can give you a general understanding of the condition of your transmission by examining the used oil. This article will outline how to replace the transmission oil on Audi A6 C6 models.
Materials Needed
- Floor jack and jack stands (4)
- Breaker bar
- Metric hex (Allen) socket set
- Transmission fluid filler pump
- 4 liters of Audi approved GL-4 75W-90 gear oil
- Catch pan
Step 1 – Lift vehicle
In order to access the transmission for a fluid change, the vehicle must be lifted off of the ground. This can be accomplished by using a floor jack and four jack stands, or a vehicle lift if one is available to you. Regardless of how the vehicle is lifted, it is important that the car remain level to ensure that the proper fluid level is achieved when filling the transmission.
Pro Tip
Take into account that this job must be completed underneath the vehicle, so be sure the lift the car high enough off of the ground to allow for sufficient working room.
Step 2 – Drain transmission
With the vehicle lifted and sitting level, proceed with draining the transmission.
- Begin by removing the filler plug located on the driver's side of the transmission just below the CV joint (drive axle). Removing this plug prior to draining the transmission will not only allow the oil to drain much easier, but ensures you will be able to refill the transmission before you go about emptying the old fluid.
- With a catch pan handy, locate and remove the transmission drain plug bolt from the underside of the transmission. Allow the transmission to fully drain before reinstalling the drain plug.
Figure 2. Filler plug located on side of transmission by axle output flange. 
Figure 3. Oil draining after drain plug removal.
Pro Tip
Audi has a very specific oil capacity for their transmissions. Many individuals opt to measure the amount of old fluid drained from the transmission prior to refilling to help gauge the proper amount of oil needed.
Step 3 – Fill transmission
- After the oil has completely drained from the transmission, install the drain plug and torque it to approximately 25-29 ft/lbs.
- Fill the transmission with fresh oil through the filler hole. This can either be accomplished by using a commercially available fluid pump to push oil into the transmission, or by routing a length of hose through the engine bay and pouring the oil through the hose and into the transmission filler hole.
- The fluid capacity of the transmission is approximately 3.2 liters of 75W-90 gear oil. Audi specifies that the transmission be filled until the fluid level is 1-3mm below the lip of the filler hole.
- Once the proper oil level is achieved, replace the filler plug and torque it to 25-29 ft/lbs.
- Lower the vehicle off of the jack stands or lift once finished and enjoy the improved shifting action of your transmission.
Figure 4. Example of fluid pump. 
Figure 5. Example of gravity filling via hose from engine bay.
Pro Tip
Unless otherwise noted, GL-4 gear oil should be used in Audi manual transmissions as the additional additives and higher sulfur content of GL-5 gear oil has been known to cause accelerated component wear.
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