Official word from MB on the 722.6 tranny is that it is a permament fill of tranny fluid. I changed mine at 70k miles. It has a drain on the pan and torque converter. Remove the pan to access the filter and then refill. You must use the special MB synthetic fluid. You also must know the tranny fluid temperature and purchase a dipstick as the car is not provided with one. Getting the fluid level right on this is very critical and not as straightforward as other trannys.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record