I have a 2005 Vectra Elite CDTi 150, I got it last March (2009) and it had 11400ish miles on it, I has now got around 120000ish. About 6 months ago I noticed (while sat in a McDonalds drive thru) that if I rested my foot slightly on the clutch pedal there was a knocking/vibrating sound came from under the bonnet. To be honest I pretty much ignored it and put it down to one of those things on a high milage car.... Anyway, last week I ran an erand for the Mother-in-Law, in the form of towing her 19 foot caravan from Penzance in Cornwall to Pickering in North Yorks (started in Leeds, so total journey about 1000 miles), anyway on the way back while pulling the caravan, if I was in 5th or 6th gear and I put my foot down there was a groaning sound from the engine/gearbox, this seemed to get worse throughout the journey. When I have got home, whenever I start the car up now and it is ticking over, there is an intermittent knocking and it is deffo coming from the gearbox, I also still get the groaning sound when I put my foot down generally in 4th, 5th or 6th gear.
I know I've gone on a bit but thought i'd get all the info in there... Does anyone have any ideas???