Adam Van Lewen

Hello, I have a ‘12 (C7) A6 3.0T with 85K on the clock. Just had the transmission fluid changed ($600, ouch) and am now wondering about the differentials. My local Indy shop told me that the front differential uses the same fluid as the transmission, and that the rear is about $80 to change.

That doesn’t sound right, does anyone know?

Got_boost

It's most definitely not the same oil as the trans. The front and rear diff use the same oil and the center diff used another oil. I know it was 75/90w oil for both but one was gl4 and the other was gl5. There is a thread going over the details of all the oils needed and walk thru's to do the jobs but I don't have it saved anymore.

had to fish around but here is a thread about it,not the same one I remember using but it does go over the same details.
https://www.audizine.com/forum/showthread.php?t=808636

5000S

Just leave it, it will outlast the car.

Adam Van Lewen

Guys at the shop said something about a transaxle, and I was super confused. They didn’t seem super confident in that answer. I find a lot of stuff for the C6 but not the C7. Thanks for the link!

KevinGary

I get the fluid in the differentials changed every 70k miles. It eliminates the Quattro rumble every time.

5000S

It is a lifetime fluid, so it should outlive the life of the car. I would not worry about it.

Got_boost

Just like the ATF if "lifetime"? Audi says it's lifetime but ZF was called and was asked about that, they said it should be replaced around every 80k miles if I remember right. Its everyone's personal choice but I'd rather spend money to do preventative maintenance than roll the dice and hope it lasts.

Adam Van Lewen

Lifetime my eye, are you nuts? On a luxury car? You know what happens when you ask the engineers what the lifetime of the car is? WHEN THE WARRANTY EXPIRES. Shush.

Got_boost

Exactly, long enough to make it thru the warranty so when it does have a major melt down,and hopefully it's brought to a dealer, they can persuade the owner into buying a new car instead of spending the big money to repair it. This is why I stay on top of maintenance no matter what they say. Oils break down over time and need to be changed at some time/mileage interval.

payedmercenary

Front an rear differentials take synthetic 75W-90 gear oil. The center transfer case takes a special 75W-90 gear oil. Part number is G 055 145 A2. I'm not sure what makes it different but it is priced as though it is liquid gold.