Drive clunking noise and vibration

[John Wainwright]

Hi all, our Q5 has developed an intermittent drive related noise under the car over the past few months which I can only describe as similar to the clunking noise a rollercoaster makes going up the hill but a bit quicker. It’s also developed a vibration from the rear, again intermittently, sometimes in 4th around 30-40mph and 6th around 50-70mpm. When pushing the clutch in it goes do drive related. It’s been in to the local garage and they couldn’t find anything obvious. Has anyone else experienced this or know what it is? I need to get it booked into an independent Audi specialist but that’ll be after Xmas. 
it’s a 2.0tdi 140bhp MY11 on about 125k miles. 
thanks in advance. 

[Steve Q]

Could it be the exhaust banging on the underside of the car? 

Or engine or gearbox mounts