I know this is a long time from the original post on this topic but had the exact same clunking noise in a BA XR6 and now have a 2014 FG XR6 same clunking noise , took literally years to find it in the BA believe it or not it WILL be the REAR CONTROL BLADE BUSHES . The original Ford ones are sh*t , replace the whole blade and bush with Super Pro products and your noise will instantly go , FG with 55000 k's same problem , Ford said nothings wrong , replaced them , noise gone , don't waste your time chasing anything else . From BA to now FG all the arse ends are the same . Every one heads for the diff bush and unless the car has had hell flogged out of it , it won't be that bush .