Hello all,
I'm new to the world of Mercedes but am learning quickly. My S430 2wd 7 speed has 106k miles on it and is in great shape, kind of. I bought it pretty inexpensive knowing it had a transmission issue thinking my ability and willingness to learn would pull me through. My car had been in an accident and the transmission cooler in the radiator was damaged where glycol was contaminating the fluid causing it to act very strange. The fluid was dark but did not have the frothy pink like it had much water in it. So now has been repaired, flush and filled to the right level with new fluid. Transmission seems to be shifting good now where it wasn't before, but now I'm experiencing a little different issue. Once the transmission is warm, it randomly wants to slip. Seems like it is always under light load or acceleration after having no load. For instance once the transmission is warm, Stopped at a stoplight and make to accelerate, it will act like it is not in gear, then jerk a little as it is trying to engage. Or if I'm cruising along and have so slow down so I'm off the throttle, then return to accelerate it will act like it is not in gear, often jerk as it is trying to engage.
It is giving me codes 2505 and 2502. I understand there are software updates for this 722.9 and that it addressed torque converter lockup function. I also had all the shift adaptations reset when I did the service. By my simple thinking it feels like there is a solenoid that is not operating correctly, but when I had it open to service it I check and cleaned all the solenoids and they all ohm tested good and their screens were mostly clean. So I guess here are the questions.

Does this sound like the type of issue that would be consistent with having need for software update and would that likely correct the issue?

Will doing the shift adaptation and torque converter adaptations help this issue?

Could one of the solenoids be bad and cause this when hot? Even if it ohm tested good?

Thanks for any input. And fire away with any questions as I'm sure there are blank spots in my post.

control issue on the interior plate. can only be fixed by dealer as it must be programmed.
Good luck!

That's good to know. What exactly is the control issue? I alway like to understand what is causing the issue, and what the change in software is doing. I don't mind taking it to the dealer, they were the ones that identified the glycol contamination.

So just going back and reading the reply. Is this a fault in the conductor plate? If so, I haven't seen any of the codes from the typical speed sensor failures, and it hasn't gone into limp mode. Is there a repair, that needs to be done to the conductor plate of just a reprogramming of the TCM?

mb suggests having the conductor plate changed out at 100,000 miles. you might look into that.

I've done a bunch of research and pulled up A lot of documents trying to pin this down. I haven't seen anything on a milage for replacing the conductor plate, though I did see some specific diagnostics for pinning down the sensor issues in the conductor plate. Do you have a TSB reference?

i had the same issue, i changed out the conductor plate and my issue never happenned again.

My understanding is that you have to change the whole valve body if you are swapping the plate on these early model 7 speeds. Did you have to change the whole valve body?

Don't mix 5 and 7 speed transmission problems.

Hi kraut, are you saying that the dealer has to swap out the plate or that they simply need to reprogram it?

The 7 speed plate can only be programmed by the dealer.
Get a transmission shop to verify the problem before you throw money at it.

I guess that is what I was looking for here, someone that could verify by codes and symptoms, what the problem is. Or at least what is probable.

Don't want to take it somewhere and they say, needs a software update, so I pay to have them update it without it getting fixed. then they say is need TCC and shifts need to be adapted and I pay them to do the adaptations and it does not fix it. So then they tell me the conductor plate then the valve body, then the internal. I'm not a big fan of paying the dealer or an independent shop to "try to fix things".

If it is likely that a software update could resolve the current issue based on these codes and symptoms, then that is what I will do. If not, then I would like to start with what is likely.

Thanks for all the help so far.

No software update is going to help you

if you don’t want to go straight to a new transmission, the steps are replace conductor plate ,then if that doesn’t fix it replace valve body , if that doesn’t fix it exchange transmission . Sorry there is no cheaper way to do it

I appreciate the info. Dealer is telling me they want to bring it in for possible software update and shift adaptations. I think that will just be a few hours of labor that gets me nowhere.

On to the conductor plate, I thought these early models had to change the valve body and conductor plate as a unit.

Is that accurate?

3 members have clearly told you what to do / what the problem most likely is, yet you keep looping back to what YOU think should be done.
Take it to a transmission shop, as stated and have them diagnose it.

Right now, it sounds like you're just seeking the solution that you want. Good luck.

Thanks for the input, I guess I read it differently and that why I was looking for more input.

One post said I needed to take it to a dealer because they have to reprogram the TCU.

One said no software update will help it and that I should start replacing parts starting with the conductor plate.

Many have stated take it to a shop to diagnose. As I stated in response, I am trying to do some diagnostics on my own so I can either work on it myself or at least know if what the dealer/shop tells me is within reason and I'm not just paying them to guess.

Once there's glycol in the transmission it's ruined, period. You need a new transmission and torque converter. Dealer price around $9,000 or transmission repair shops, if you can find one who will work on it, maybe $3-$5,000. A used transmission will not work without replacing the control unit/electric plate as it's VIN locked. Again, that's $3,000 or so. Repairs will likely exceed the value of the car.
Here's my expert advice... sell the car as-is, trade it in, or part it out.

This is not correct. Nowhere does MB suggest this.

I was under the impression that water did the damage to transmissions rather than glycol?

Symptoms are not consistent with water damage. Acts like a control issue, hydraulic or electrical. Would hate to rebuild the transmission and have it act the same once rebuilt because the same conductor plate/tcu has to be reinstalled in it.

You asked for expert advice, I gave it. As others have pointed out, you're not listening. Best of luck to you.

Just trying to understand. That is why I ask. Everyone is great in providing suggestions and I am thankful. I have seen al lot of bad " expert advice" dished out on forums, (like replacing the conductor plate at 100k) so I am trying to understand the method behind the madness. Thanks again

In your 1st post, you stated that the ATF was contaminated with gycol and that the transmission was repaired (repaired how)?.

It is S.O.P to replace clutch friction plates after any glycol / water contamination and also flush out or replace the torque converter
If the frictions were not replaced, then the transmission will slip. WHY WOULDN'T THEY??

No reprogramming is going to 'repair' the damaged friction plates. Wishful thinking and non-productive.

I'm not going to play a semantics game but yeah, it's a control issue ----> slippage.

I guess a little clarity. The radiator/ transmission cooler was repaired, atf and coolant were flushed and filled. I did the work and was advised to do so by the Mercedes dealer. I agreed this was the best course of action since the fluid looked dark from the glycol contamination but did not appear to have standard water contamination as the fluid was not light or foamy.

I agree that with water damage, friction discs should be replaced as the water can disintegrate the lining. It doesn't seem to act like water damage.

If the transmission were slipping, I would not have brought it up because, yeah the internals are shot and it's time to open it up.

When under high torque there is no issue. In my experience with transmissions the high torque would make it slip if it were going to. It doesn't. Only time I see any issue is after it comes to full temp, in low torque periods it acts as if it is disengaged, then will get a little jerky like it's "trying" to get engaged, like there is some kind of electrical or hydraulic fault. When it is engaged, there is no evidence of any slip.

From your 1st post: "Once the transmission is warm, it randomly wants to slip". You just checkmated yourself! ----> The latest: "If the transmission were slipping, I would not have brought it up because, yeah the internals are shot and it's time to open it up."

Did you even bother to read what those 2 trouble codes mean?? As a Master Tech and advanced transmission builder, IMHO (I don't mean to sound rude or like a jerk), you have no idea what you're talking about. Stick a fork in that transmission, it's done!

No, stick a fork in this thread; it's done.