I recently had a problem with my E350 where it started shifting hard between 2nd-3rd gears, then wouldn't move at all because it seemed to be stuck in 2 different gears at the same time. I found that by setting the transmission to Comfort Mode (C) with the engine at operating temperature, it would go into 2nd gear but would not shift. When it was in Performance Mode (P) it had 2 gears engaged at the same time and would move if I really stepped on the gas and one of the gears slipped (not good)! When I got the car going over about 25 MPH in C mode 2nd gear, I could put the selector in neutral and then back to drive, and it appeared to go into 6th gear.
Hmmm... Sounds like a major transmission problem, right? I decided that it was most likely something to do with the valve body or the transmission computer, which is built into the valve body. I drained the transmission fluid and removed the valve body. The bolts that hold the valve body on are the ones on both ends of the body. I also disconnected the electrical connector that connects to the valve body. I then dropped the valve body onto some clean shop clothes that were on my chest as the car was on jack stands and I was directly under it. I wanted to be very careful not to drop it or to get ANY dirt or contamination on it.
After removing the valve body, I removed the solenoids, and lo and behold, one of them had a broken o-ring, as seen below:
Pieces of the o-ring had actually gone into the valve body and required me to remove the plates that contain the valves in order to clean the bores and valves. I took pictures of all the valves and springs as I removed the plates to ensure that I got them back in the right way.
The contacts and everything on the conductor plate appeared to be fine, so I cleaned everything very well with brake cleaner (I used brake cleaner to clean the valve body, valves, and bores as well).Mercedes does not sell the O-rings specific to this application, they will sell you an entire valve body. I went to Harbor Freight and got a set of metric O-rings which contained about 250 assorted O-rings for $3.00 and replaced all of the O-rings on the solenoids with those.
The total cost was still quite expensive as I replaced the transmission fluid that I had drained and the filter. I didn't drain the fluid from the torque converter this time as I had done a fluid change recently. The fact that I had changed the fluid recently leads me to believe that the previous owner had not changed the fluid because this is the kind of thing that happens when you change the fluid in a car that hasn't been serviced for some time. The total cost was about $135 for everything. I use Redline D6 full synthetic transmission fluid, not an endorsement, but I have used their fluid with good results in the past in other cars.
I will describe the method I use for changing the transmission fluid in another post. I hope this helps someone! It saved me a lot of money over taking it to the dealer and getting stuck with either a new valve body or even a new transmission...
