I have decided to do this on my V85 TT (E5) much earlier (at 5,000 km) than specified in the maintenance schedule (at 30,000 km). I change the gearbox oil when the engine has warmed up (drive at least 40 km) to get as much out as possible.
The gearbox should contain 700 ml oil, but my contained approx. 550 ml (quite a lot of metal shavings on the magnet and also some in the oil, not quite as dark as the oil in the final drive).
The final drive, should contain 160 ml oil and my contained 160 ml (no metal shavings, quite dark).
Sealing washers and o-ring part numbers
Final Drive: 224566, GU01528930
Gear Box: 287174, GU10528900
O-Ring: GU90706203
I just needed one new washer for the gear box (drain plug)
Oil SAE 75W-140 - API GL5
Gear Box: 700 cm³ (ml) or 42,72 cu in
Final Drive: 160 cm³ (ml) or 9,76 cu in
After the first ride since changing the gear oil, I can confirm that the transmission shifts more smoothly and has become quieter (the "humming noise", similar to that of the Michelin Anakee Adventure tires).