2010 TDV8 - 65k miles

last January i posted on here about a strange vibration. the vibration persisted and i took it into local main agents a month ago but they said they couldn't detect anything. today the problem got a whole lot worse..

driving along about 20mph and suddenly the engine starts to make a lot of noise. in fact the revs had gone up and the car was slowing down. coasted to a halt and switched it off. started engine again and i think the engine is fine but if you rev it from idle whilst stationary there is a kind of hiccup as the revs rise. haven't tried driving any further so LR came to collect it on a low loader.

these are the symptoms it was displaying prior to today:

1. At any road speed when very light feathering of the throttle there would be a slight ‘clonk’ which felt like a small amount of backlash in transmission. At some specific speeds (e.g. exactly 70mph and exactly 52mph) the effect was more pronounced. As well as the backlash effect, there was also a kind of ‘whirling’ or quivering sensation after lifting off the throttle which I considered similar to a shaft running out of centre. This whirling effect commenced about 1/2 second after lifting off the throttle and only for about 1 second, gradually diminishing over the 1 second period (a little bit like non- damped spring).

2. When driving though town and e.g. approaching traffic lights which are Red, you might ease off the throttle to allow the car to coast to a halt. Suppose the lights changed to green during this coasting phase you would press the throttle again and depending upon the delay between easing throttle and reapplication, there may be a pronounced feeling of backlash. The presence or absence (or magnitude) of this could be managed by foot pressure so could essentially be eliminated by driving style.

i guess i should know soon what the problem is and what the cost. any guesses?