Long time no postings on this issue...
Maybe I can give some good advise backed by own experience:
I had a quite noisy BB & belt unit and was not sure where all the squeeking and whining was originated. Some definitely comes from the bevel box and when the oil gets warm noise is always there.
I finally located that most noise was generated from the drive belt.
Lots of silicone spray did reduce the whining but only for limited time and/or milage than the noise came back.
Today I dismanteld the rear plastic cover and used a high pressure sprayer to clean the belt and both spockets. I used a car jack to lift the rear end and run the wheel in 2nd gear and thoroghly washed the system. Great result: nearly all the noise is gone. When I had a short drive for drying the rear brake I was amazed how quiet the whole drive system operated.
I am sure noise will come back when dirt settles on spocket and belt but now I have a good solution for my TW: High pressure spray cleaning works on mine.!
