Diff and transmission fluid data points?

[Eatpocky]

Have been planning to replace my diff and transmission fluid in my B8.5 A5 with a ZF-8 but most of the threads I've come across have varying information, outdated or no follow up.

In the interest of consolidating information, I was wondering if folks would be willing to share their experiences with different fluids when replacing their diff and transmission fluid.

Front/Rear Differential Fluid:
Seems like the general consensus is our cars are ok with any 75w90 GL4 gear fluid. Any experiences where our cars don't like a certain brand?

Center Differential:
This one seems a bit more controversial due to the nature that Audi has a specific fluid (G 055 145 A2) for the center differential. I've come across multiple threads suggesting either:
- you can use 75W-90 with 4% Ford XL-3 (https://www.audizine.com/forum/showt...fferential-oil)
- You could probably just use Valvoline SynPower 75W-90 and be completely fine since it already has friction modifiers (https://www.audizine.com/forum/showt...fferential-oil)
- Any 75w90 GL5 fluid since newer fluids have FM's compared to before (https://www.audizine.com/forum/showt...fferential-oil, https://www.clubtouareg.com/threads/...change.287093/)
Thoughts?

Transmission:
Based on research, the ZF8 is strongly recommends using Lifeguard Fluid 8, but seems like folks have used other off the shelf brands. Any experience?

Thanks!

[hahnmgh63]

You are correct in most things above except you also want a GL5 for the rear Diff, not a GL4 (fairly big difference) I have used Redline D6 in place of the Lifeguard 8 in previous vehicles but when I just changed the fluid at 45k in my wifes SQ5 I used the ZF Lifeguard 8 and a Mann Filter. For the center Diff I have used Redline 75w/90 with no issues.

Great thread here: https://www.audizine.com/forum/showt...ht=DSG+Service