My 300td slips in fourth gear only, 1,2 and 3 are fine. I knew this problem existed when I bought the car, the fluid / filter has been changed and the fluid is at the correct level. When the car is in "S", it shifts fine..no slippage. But, when in "D", and it goes into fourth gear, if you drive at normal pedal depression, its like being in neutral. If I feather the throttle, like on flat ground, or down a hill, it does ok in fourth. I can get a good run down a hill, and run 60 or so on basically flat ground. But, there is a point when I guess the load is too much, and the transmission will slip. I let off the throttle, it goes back into gear, and I have to lightly give in throttle or depending on speed, put it in third. Is fourth gear in this thing a stand alone friction deal? Is there anything else I should check, or is fourth gear basically just shot?