Td4 Engine mounts

I haven't had chance to get under the car yet but over the last couple of weeks I have been getting a bit of a clunking when changing gears probably up to 3rd then it seems ok. I am almost 100% this is the engine mounting. I seem to remember reading something about how best to check the mounts on a TD4 I have searched but cannot find it. Anyone any ideas?? I am certain it is not the diff mounts.