acmathis61

Searching the forum and reading the Bentley provides conflicting information on the fluids used for these gearboxes.

From what I can find in the Bentley and on the forums, the transmission/centre diff/front diff all share the same fluid, and combined use 2.85 litres of SAE 75W90 G50 gear oil (Redline seems to be the most popular, but Motul Motylgear 75W90 is reported to quiet down notchy transmissions better, so I likely will go with that)

For the rear diff, the notes in the Bentley (Fiche No. 6, illustration 39.28) seem to indicate it uses 2.75 litres of SAE 90 GL-5 gear lube, meeting MIL-L-2105B. It would seem that any high-quality synthetic 90W GL-5 gear lube would be appropriate for the rear diff. However, several users report using SAE 75W90 in the rear diff.

With regards to the rear diff, is 2.75 litres the correct amount of fluid, and does anyone have any comments or suggestions regarding using 90W vs 75W90?

Thanks for your help.

squidix9

NEO 75-90 RHD which is GL-5

Can't help you on the volume though, my rear ends are different than yours<ul><li><a href="http://www.neosyntheticoil.com/products_ge.html">NEO Gear oil</a></li></ul>

4AudiQ

I just put in less than 1 liter (1.6pints) 2 hours ago. Mine is a 1995 Audi Sport 90 Quattro:
Transmission = 3 1/8 liter (6+ pints).
Differential = less than 1 liter (1.6 pints)<ul><li><a href="http://www.motorspot.com/">http://www.motorspot.com/</a</li></ul>