6th gear drive train vibration - 2005 Verso 2.2

[Keverso]

I have a 2005 2.2D4D Verso and recently it has started developing a vibration in the drivetrain but only in 6th gear at low revs. Accelerating is fine and driving in town also, but when going to 6th gear under 120kph (between 70 and 80mph) i get quite a lot of drivetrain vibration which does diminishes as i accelerate, with it being nearly completely gone at 200kph. Obviously this is a pain as I am concerned that I am going to damage something, as the vibrations are qute bad and with normal motorway speeds being around 120 I would like to be in 6th gaer for economy.

Does anyone have any ideas for me? It was recently serviced but the dealership did not see anything obvious, but also did not test drive it due to lack of time.

[Heidfirst]

I take it that you have checked all your tyres for damage/out of true/balance?