My 2010 hdi auto may have a possible fault when changing from 2nd to 3rd gear, all other changes are silky smooth and appear normal, but the pronounced thump when changing from 2nd to 3rd, the c5 has 26k on the speedo, the car is booked in for 13/05, should the so called sealed for life gearbox need new oil or filters or both should I have to pay for this service, (cant wait for the blame game to start), any advice would be appreciated regards Tony.