[Farther]

I have found two sources that say to change the differential gear lube (not talking about the ATF) in the VW:

Wikipedia entry:
transaxle.https://en.wikipedia.org/wiki/Volkswagen_01M_transmission
This transmission has a separate oil for the differential in the transmission, so there are two fluid levels to check. The differential fluid is checked by unscrewing the speed sensor gear assembly and use it as a dipstick. The speed sensor gear assembly is located on top of the transmission just above the right inner CV joint. Differential is emptied by removing the final drive cover on the rear of the transmission or by vacuum extraction through the speed sensor hole. Vacuum extraction is the more attractive option since a paper gasket seals the steel cover and access is very difficult. Filling is through the speed sensor hole. Differential oil capacity is about 1 liter. An acceptable differential oil is Redline synthetic MT-90 75W90 gear oil or any synthetic 75W90 GL5 gear oil. Be very careful not to introduce sand or dust into the differential, as the differential has no way to filter its oil

GoWesty Maintenance Schedule:
http://www.gowesty.com/library_article.php?id=1424
MILEAGE SERVICE
Every 15,000 miles - Trans fluid service
• Gear oil change in differential section
• Automatic trans service, fully synthetic ATF and filter

When I told the VW dealer to change out the differential lube in the transaxle I got a a short lecture from the male service advisor (not the one that normally helps me) on how there is no differential lube in the transmission. 

Anybody please advise.

[Itsamoto]

You're on to something here.

In the EV Bentley -- the distinction of the fluids is not explicitly clear. It does list separately the "planetary transmission" @ 5.35L capacity of VW ATF (G052162A2), and the "Final drive" @ 1.15L of SAE75 W90 synthetic gear oil.

It notes that the final drive as "filled for life". 

[Itsamoto]

Bentley also mentions checking the "final drive" oil level -- removing a plug to an indicator hole on the backside of the transmission (accessible through a space in the subframe ). 

Fluid level can be topped up to being just up to the edge of the indicator hole.