MrMeredith1

Hello, I have been told two different things from two different mechanics about this. Is it recommended that you service the transmission every 40k miles? Thanks for any clarity you can provide. One of the mechanics stated it was a sealed transmission and there is no way to flush/ service it.

Rudeney

Your MY2004 CLK320 has the 722.6 5-speed. It was sold as "sealed for life", but don't believe that. After some failures, MBZ issued a bulletin to dealers stating something along the lines of, "If customers ave concerns about the transmission, then it's acceptable to do a fluid and filter change at 70K miles." Then, they came out with the 722.9 7-speed. It was also sold as "sealed for life", but they started seeing some early failures due to deteriorating clutches in the torque converter and fast-wearing sleeve bearings int he fluid pump. So, they issues an official bulletin for a one-time 40K mile fluid and filter change to help get rid of that "break-in" particulate. Later, they went with a service schedule of every 40K miles.

Having said all that, I don't think the 722.6 really needs a service every 40K miles. Doing a full change AND flush every 70K is probably adequate, and there are also many thousands of them on the road with 200K miles or more that have never been serviced. Note that most 722.6 transmissions do not have a torque converter drain, so to do a proper fluid change, you need to do a flush. If all you do is a pan drop and filter change, you'll get less than half the fluid out. In that case, maybe every 40K is a better schedule.