boll++++ my tentioner was sha++ed and it only showed its self whilst under loadMust be wheels/transmission if as u say "It's only while driving".. Aux belt or any thing engine related would be all the time it's running.
Sounds like a bird. Seems to disappear when I press clutch! Fitted new clutch kit in june
Bought 2 britpart ujs today £20.40 just got to find time to fit them.