Hi driving on the motorway to the alps and my 2010 vogue 4.4 tdv8 75000 miles then the car made a knock or thump which felt like we had driven over a pot hole. Sound felt like it came from the rear, but difficult to tell. Then straight away there was a reduced performance message and slowed to 60 miles per hour. Stopped at the services and filled up with fuel then all was ok. Carried on for 6 hours to resort with no problems but took it easier. Previous to this I had noticed a knock when easing off the power similar to an engine mounts wear in old cars. Any ideas what this Is?