Passat tdi Diff whine

[Pizzainmay]

New to this forum but owned VW's for 20 years.

I have a W reg 1.9 tdi Passat estate with 134k miles and am getting a whine whilst driving, this is generally more noticable when the clutch is in and the car still moving but also noticable when engine power is taken off (over-run).

I have searched various forums and they seem to indicate a faulty diff although some have simply said change and or top up oil.

Questions:

Has anyone else out there had this problem?
Does the oil change thing work?
How else have you 'fixed' it and how expensive was it?

Any help gratfully received

[Pizzainmay]

Anyone????