Nickthegreek

Hey everyone. So after reading a lot of posts on the forum and also owning a 07 ml350 and 09 s550 with the 722.9 tranny and seeing similar posts about the transmission failing on both forums, i thought about starting a discussion about what might be the issue going on here.

Does anyone know if the cause of failures can be pinpointed to any one cause and if so is it preventable? It seems like certain year models are more affected than others and in my opinion I wonder if not changing the transmission fluid during the initial break in period could have alot to do with it.

The major issues I know/have read about are:

1) hall effect sensors on the tcu being faulty needing to replace board

2) connections going bad and shorting

3)valve body

Im wondering if debris from ferrous metallic particles could be contaminating parts causing them to fail early. I decided to put two 90lb magnets on my tranny pan a while back when i did my transmission fluid just as good measure. I havent had the transmission problems with any of my vehicles but there are many others who have.

Also they used to swear by never having to change transmission fluid for life. Anyone know when they stopped saying that? I wonder if that could have a lot to do with transmission failures

konigstiger

MY09 changed from once @ 39,000 to every 40,000/4 years (whichever comes first).

Nickthegreek

Thats interesting info because alot of the problems seem to happen pre-2009. This article also reiterates how important regular fluid changes are and how transmission maintenance is lacking with alot of these transmissions. Gonna look for more articles but it seems that the key is to look at past maintenance history of the transmission. When I got my car it had 50k miles no it and no issues so I immediately flushed the fluid and put magnets because there was no prior history of transmission fluid changes. Now when I had gotten my 07 ml350 i never bothered to see if it had regular maintenance done in it and it had 72k miles on it. when I went to change the transmission fluid it was black so i disconnected the cooler line and over filled the transmission by 1l then pumped 2 out put 2 back until it was cherry red then topped the fluid off. Never had problems with it and drove it until I had 110k miles on it without problems.

http://www.datsc.com/Mercedes-Specia...nProblems.aspx