My 92 300D 2.5 turbo has over 300,000 miles and tranny has been slipping for a while now, but lately it is slipping more. It would just slip when in reverse, sometimes from 1 to 2 shifts. Now it seams to be all that but more in forward now. I know how to firm up the shifts by turning the vacuum control valve on the tranny, I turned it two notches clockwise, I will see what that does. Fluid is full, changed fluid and filter not too long ago. Just to be sure, you check tranny fluid with car is warm and running and in park? I cant remember if you check in park or neutral.