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2007 SLK350
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Just went through transmission issue and did a lot of research on what/why this happens in our SLKs. My car is 2007 with 102K miles. I got it about 6 months ago and it was several months before I had the first malfunction. After comparing other descriptions of transmission failures it appeared to me the most likely cause was a problem originating from the Conductor Plate.

After finding out what is involved with this project I decided it would require tools and experience that I did not have, so I found an independent shop that was MB authorized and had the Star Tek terminal (connected to the MB database) and lots of experience with the 722.9 transmissions. It seems this transmission, although used in several other models, is known for this type of failure. On the positive side, unless the transmission is abused, the gears, bands, and clutches seem to hold up fairly well.

Once I decided to repair the fault the first thing was to check for fault codes. Sure enough the fault code "Communication Failure in speed sensor" was found. Since this happened only a few times over several months I decided to drain and flush the tranny. The mechanic said in some cases this would clear it up, however, eventully the conductor plate electronics would become a hard failure. After changing the fluid, I drove it for about 2 hours and it went into the limp home mode. I returned to the shop and left it knowing it would only get worse.

The fault code was back, so I made the decision to replace the conductor plate. This also includes a computer module (Transmission Control Unit TCU) that is mounted on the bottom of the conductor plate (that is part of the plate assembly) and is submerged in the oil. Additionally, there are 8 solenoids 4/4 side and 2 speed sensors imbeded in the rear of the conductor plate and are located just below the main cluster gear in the transmission. These 2 speed sensors count the revolution of the splines to monitor the speed to determine the proper gear selection. Their output is sent to the TCU, whcih also monitors engine RPM, wheel rotation speed as well as a number of other inputs to determine gear selection and shift points.

In my case the speed sensors were having trouble maintaining the signal reads of the splines because the oil had become so dirty it was partially clogging the magnetic sensor reads. The mechanic pulled the conductor plate and removed the valve body, separating it to remove the check valves and clean it internally. The new conductor plate comes with new speed sensors imbedded in it, as well as a TCU. Once the valve body and conductor plate were mated back up it was installed in the transmission.

I should also point out the conductor plate is considered a Theft Relevant Part (TRP) by MB. What this means is; the dealer most likely will not sell it to you. They (MB) does not consider this a part to be installed by the owner. MB will sell it to their authorized independent service centers, however I had to supply ID and proof of ownership just as you might have to do in getting a spare key.

Once the conductor plate was installed, it requires programming. This is where the Star Tek terminal and experience of the mechanic are of benefit. Since the TCU interacts with the Engine Control Unit (ECU) programming is an important part of this process.

In discussion with the mechanic that did this transmission work he commented this is a fairly common problem with the 722.9 transmissions. He recommends a flush and refill every 50K period. He also noted the conductor plate failure, one it starts, will typically get progressively worse until it completely fails.

While I do not profess to have the all the answers, I researched the threads and all the info I could before making the dreaded conductor plate repair. Since I have gone through the process I have been quite pleased with the results and smooth performance. While there are no doubt more experienced DIY individuals in this group, I suggest you make sure you know what you are taking on before attempting this yourself.

I posted this in hopes that it will help provide some insight as to help you get a better idea what is going on with regard to common conductor plate issues.

Lknman
 

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I live in Troutman and also have a 2007 slk350 with 102,000 miles. My car went to limp mode once last summer and yesterday did not want to go in reverse & through a code (speed sensor not reading). My question is what shop did you use and how much did it cost?
 

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2007 SLK280
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52 Posts
Conductor Plate replacement in Toronto

I've just had my conductor plate (CP) replaced. ('07 SLK280, 80k km)

I went to a well known MB independent in Toronto/North York, I paid $1,600 + tax. (Incl. Mercedes transmission fluid.)

I shook my head, when the owner said he had the conductor plates in stock. He showed me a newish E-series sedan, jacked up for a conductor plate replacement. (He said the CP problem is still happening on MBs ...)

As a frame of reference the local Mercedes dealer wanted $1,900 + tax.

(PM me, if anyone wants the name of the shop.)
 

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*Premium Member
2004 SLK32 AMG
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5,640 Posts
I live in Troutman and also have a 2007 slk350 with 102,000 miles. My car went to limp mode once last summer and yesterday did not want to go in reverse & through a code (speed sensor not reading). My question is what shop did you use and how much did it cost?
Always nice to know where a good MB Indy is. What shop did you use?
 

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2007 SLK280
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52 Posts
I went to a dealership in Burlington area and I got a quote for $1180 + taxes. That's for 3.5 hour labor and parts..
That is a great price - jump on it ASAP. (I was told the CP part alone was $600, and new MB transmission fluid change was $450 at an MB dealer. The labour sounds about right.)

The local North York MB dealer quoted $1900 + taxes for the CP plate replacement.

Another member asked about the independent I had used. They are McNally Auto, another slkworld member told me about them. They are MB specialist.

McNally Auto Service ? Full-service automotive maintenance repair facility
 

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2006 SLK55 AMG
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352 Posts
you guys are lucky to have gotten that kind of mileage out of your cars before having the issue. I first got it a year ago at 25k miles, and it's pretty bad now at 30k. Bringing my car into an independent shop thursday, costing me $1400 to have it fixed. Probably would cost $2k at the stealership.

As a side note, there are very few independent auto shops that can do this install, probably fewer that can do it competently. So I would make sure you get the work done by a shop that primarily works on MB.
 

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*Registered
2006 SLK55 AMG
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352 Posts
I live in Troutman and also have a 2007 slk350 with 102,000 miles. My car went to limp mode once last summer and yesterday did not want to go in reverse & through a code (speed sensor not reading). My question is what shop did you use and how much did it cost?
All you have to do to reset it is turn the car off and on. If you're having it happen that infrequently, I would wait until it happens more frequently, but that is just my opinion. It will gradually get worse and worse. Happening 1x per year isn't bad....
 

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*Registered
2006 SLK55 AMG
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352 Posts
I live in Troutman and also have a 2007 slk350 with 102,000 miles. My car went to limp mode once last summer and yesterday did not want to go in reverse & through a code (speed sensor not reading). My question is what shop did you use and how much did it cost?
I've just had my conductor plate (CP) replaced. ('07 SLK280, 80k km)

I went to a well known MB independent in Toronto/North York, I paid $1,600 + tax. (Incl. Mercedes transmission fluid.)

I shook my head, when the owner said he had the conductor plates in stock. He showed me a newish E-series sedan, jacked up for a conductor plate replacement. (He said the CP problem is still happening on MBs ...)

As a frame of reference the local Mercedes dealer wanted $1,900 + tax.

(PM me, if anyone wants the name of the shop.)
This is a faulty part. The shop Im taking to carries the part in stock also. If you own one of these cars, eventually the part will fail, probably without exception.
 

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2006 SLK55 AMG
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352 Posts
well, just got my conductor plate replaced. I'm not sure if it's a result of the non-defective plate itself or if it's due to the updated software programming, but the shifting is way smoother too. I used to have a hard shift 4th to 3rd and 2nd to 1st (common on the AMG), issues seem to have gone away.
 

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Registered 2007 SLK280
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6 Posts
If 722.9 transmission decides it no longer wants to shift gears while driving, you may be experiencing the speed sensor problem located on the conductor plate inside your transmission. Seems to bee fairly common. I just had the Conductor problem as well. P0717 and P0718 codes were presentas well. "Y3/8n1 Turbine Speed sensor (VGS) is defective." After some research, and some ridiculously high quotes to have it replaced, I decided to attempt the repair myself! Having your conductor repaired, rather than replaced saves A LOT of problems in having the car re-programmed to accept a different one. And no need to have the adaptive learning reset. And the removal and replacement was not that difficult for an average DIYer. I found a great video on how to remove it, and the same producer of the video repairs your board with a 1 day turnaround (plus shipping time).
Video:
.

After the car was on jackstands, the actual removal took about 1 hour! I cleaned up the conductor board and FedEx'ed it to circuitboardmedics.com on Monday morning, and received it back Saturday morning! Re-install also took a little over an hour, including warming the engine for the fluid level check. Board repair cost was $299

It did require transmisstion fluid, pan gasket, trans filter that I bought as a kit from FCP Euro for $85.

Additional tools were a 'Transmission fill adapter" for $15 from FCP Euro, at fluid transfer pump from Harbor Freight $8, and a couple of large, shallow plastic bins from Walmart too keep the mess to a minimum $8.

If you're considering changing it yourself, watch the video! I was pleasantly surprised how easy it was.. .and saved well over $1600!
 

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2006 SLK350
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547 Posts
Yeah but....do you get an updated transmission control module with it?

It seems to me that the conductor plate replacement is not just a repair, it's an upgrade in that it includes the new TCU with new programming.

So...sure..it's cheaper to repair (and nothing against that) but the question is, is it better to upgrade rather then repair? I'm going to likely need to do this work and I'm leaning towards an upgrade.
 

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*Premium Member
2001 SLK320 & 2000 SLK230
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2,722 Posts
Personally prefer the least intrusive methods and since I have other cars (and a lift) a week would be no biggie. The real question is whether you like the way it shifts now and how likely is infant mortality with a new one. Shop would have to eat if problem (part of the $1600) but personally would prefer the rebuilt with same ID from a trusted supplier..
 

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**Premium Member 2004 SLK350
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5,653 Posts
Yeah but....do you get an updated transmission control module with it?

It seems to me that the conductor plate replacement is not just a repair, it's an upgrade in that it includes the new TCU with new programming.

So...sure..it's cheaper to repair (and nothing against that) but the question is, is it better to upgrade rather then repair? I'm going to likely need to do this work and I'm leaning towards an upgrade.
You can always update your old TCU software to the latest version...
 

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Registered 2007 SLK280
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6 Posts
Absolutely no change in the shifting. The repair was just to the speed sensor on the conductor plate. Since there were no shifting issues whatsoever, this method seemed to be the easiest , least intrusive method. No new software required, no adaptive learning reset..... just a sensor change on the board
 

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Registered 2007 SLK280
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6 Posts
Did it myself in my garage! Six bolts hold the pan on, and 10 hold the valve body in place. Putting the car on jack stands took a bit.. but the actual fluid drain and removal took less than an hour. Required a torx bit, and socket.
 

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Registered 2007 SLK280
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6 Posts
I did find out that the conductor plate is tied to the car computer for anti-theft reasons. A new conductor plate requires a Mercedes Tech to re-program the computer to accept a different serial numbered plate. In talking to independent shops to have the work done, that process did add to the repair cost...
 
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