Gearbox Problem on C270 Auto
 

I have a Mercedes C270 CDi Automatic. Year 2001
When I use the kickdown sometimes it defaults to 2nd gear. I have to stop the car switch off the engine it then resets itself. I put it into Mercedes they changed the gear selector this did not work. I took it to an automatic gearbox specialist he changed the valve body. This did not work. I have been told it may be the speed sensor the chap who changed the valve body has said he changed the speed sensor. Now I am being told it needs a new gearbox but the car runs fine if I do not use the kick down. Can anyone help

The trans should generate a code that can be read with MB dedicated scanner..reading those codes is a GOOD starting point.