Many thanks for your replies. First I went to Merc Dealer, for a transmission fluid change. After a diagnostic test they came up with a £1850 quote. Then I went to a Merc specialist, and ask again to change the transmission fluid. They told me that the transmission in Avantgarde is a sealed unit and you can’t change the fluid, is this correct? The car is 2001 model and has done 35 K. Recently it was coming up with “Transmission Fault go to workshop” error. That is way I wanted to change the Trans fluid.