2 wks ago I've noticed my car was acting funny while driving home to and from work,the car was purchased last july with 47,000 miles on the odometer and never been to the M/B dealership since purchased from the previous owner.the car wasn't shifting right so the next day, I've taken the car to an indy shop to have it flushed and a new filter replaced.After they were done,I've drove around for awhile and noticed that the A/C wasn't cooling the car since it was hot outside(Houston heat) but later on,the car cooled down!I've kind of figured that the tranny fluid needed to get used to! But lately,for three days the tranny was running fine but then it was shifting differently like the it wasn't shifting from 3rd to 4th gear but it went away a few days ago and now its hard to shifting from 1st to 2nd gear like I was driving a 5spd!!! I'm going back to the indy mechanic to see if they had drained my torque converter or they didn't put enough fluid in the tranny! Plus check to see if I have the Velero radiator!!! I'm trying to get the car road ready for a trip to Myrtle Beach,SC!! I'm happy that you guys give great info on these cars since I'm a newbie and this is my first Mercedes from a Lexus!I've gotten this car at a great deal and I want to keep it for along time!

 

Congrats on the new purchase!

Specifically with regard to transmission servicing, there is some real confusion around what/when to service these cars. If you do a search on this forum, you'll see that the W209 service schedule was updated mid-stream and what was once 'lifetime fluid' for these transmissions was changed to recommending a 40K service interval on the trans fluid sometime after the 2004 timeframe.

My own personal experience was that after seeing the "every 40k" update, I had the fluid and filter drained and replaced in my car at 84K, it improved the smoothness of the shifts and has been in the car ever since, and all is well. Note that it was NOT a drain of the torque converter (more than 9 qts apparently), just a drain, filter and refill with fresh fluid). There's also a seal that commonly fails on the W203/W209 transmissions that costs about $15 and is an easy fix, I had that done at the time and would recommend you look into that as well.

In speaking with my indy mechanic (a retired MB master tech from my local dealer), I asked him about another transmission service, including draining the torque converter, and he advised against it - he said that given the mileage of my car (122K) that there's a ton of stuff floating around in suspension in the fluid, and by replacing all of the fluid, I would be looking at driveability problems - which is what you seem to be experiencing. I am not sure what the cure for this is, but I would seek out an MB transmission specialist either online or preferably in your area - perhaps Glynn and Rudeney have some sage advice here, but you could be in for a rough path forward.

Also, as a new (used) owner, I would strongly recommend that you take your car to your local MB dealer for a "Service Clinic" - this is a program that MB does, where they run your car through a fairly comprehensive inspection of repair and maintenance items that need to be done. You will need to do some searching around to find when your local dealers are doing this program, but it is usually a few times per year. Or you can just call your service advisor and see if they'll do this for you.

This is of course to get business for their service department, but what you get out of it is a comprehensive list of the things your car needs, along with list of part numbers (yay!) that are needed to complete the repairs. You then have a great 'punchlist' of things that the car needs, along with hard cost estimates and you have a starting point to work through these problems with your indy or the dealer. On some recent (and much needed) repairs, I had a good cost baseline from which to work with my indy.

An important consideration, at least for me, is the fact that taking your car to an MB dealer for service every 18 months and spend $100, your car remains eligible for Roadside Assistance. Hope this helps.

 

Yes, there was an informal letter (not even a TSB, just a "note") sent to dealers back in 2004 that suggested a fluid/filter change around 70K miles on these "sealed for life" 722.6 transmissions. This was based on a higher than expected failure rate when they passed 100K miles. One challenge there is that they deleted the torque converter drain somewhere around 2000 (why do you need a drain on a sealed-for-life unit, right?). So dropping the pan and changing the filter only changes 4 quarts or so, but it's better than nothing. There is a way to do a full flush, but it requires pumping fluid through the cooling lines (much like doing a brake fluid flush).

Anyhow, at that time, the 722.6 was being phased out and replaced by the 722.9, which did come with a torque converter drain. Early 722.9's were seeing problems at around 60K miles with pump failures. It was found that they had some improperly forged components throwing extra contaminates into the oil, so there was a TSB and a change in the maintenance manuals for a "one time 39K mile fluid filter change". The though is that the components would by them have "sloughed off" all their metallic contaminates, and all should be good. However, after seeing the condition of my CLK550's just a few hundred miles after a fresh change (I had to fix a gasket leak after the job), I think I will do it every 39K (maybe every 30K).

Yep, the pilot bushing seal for the TCU connector. It can leak oil on the ground and "wick" it into the wiring and contaminate the TCU. The revised seal is a permanent fix.


The whole "to change or not to change on high-mileage transmissions" is something of a touchy subject (like religion and politics). I believe a change is not a problem with high mileage, but plenty of people say it is. And the fact that you are only changing 4 quarts (about 25% of total volume) at a time in the 722.6, I can't see how that is a problem.

 

Some people experienced failures in higher mileage transmissions when doing full flushes. Supposedly this was due to sitting contaminants being stirred up and clogging the filter starving the transmission of oil.

I sold my c32 before I had to do anything but I decided only to change the fluid in the pan, new filter, seal and bushing and leave it at that. It seemed like the safest most cost effective option for me.

In theory if you did a full flush and then another one about 2-3,000 miles later you would remove the stirred up crap and prevent failure but thats a lot of work and expense. I would recommend the partial job for anyone when it is too late to do regular changes thanks to previous owners. This is especially so since you can DIY easily whereas the full flush requires a lot more work and some equipment if you don't want to make a mess.

 

Awesome stuff. Thanks Rodney!

 

I'll stick my neck out on this one. A change will always be the best thing to do. Not doing so will guarantee a short life. If a transmission fails after a change/flush it would have failed anyway. These transmissions were never intended to be filled for life. That is a North American violation of Benz intentions. Change every 39K miles or 60K Km's with 722.6 & 722.9 transmissions & 722.9 Plus with new blue 236.15 fluid every 120K Km's ~ the jury is out on how well this will work in practice. There are no CLK's fitted with 722.9 Plus transmission. Introduced August 2010 production. The 236.15 fluid is not reverse compatible.

 

I know in the MBZ transmissions, the fluid is under a good bit of pressure and really being moved around a lot, so any particulate would be suspended in the fluid. Changing it would not stir up additional particulate. However, with that suspension, the fluid would be thicker so there could be tight places where particulate could "hide". Still, releasing that can't be any worse that all the stuff already in the fluid that can keep it from getting into tight areas and even being abrasive. I'm with Glyn - I think the reports of changing fluid causing failure is just coincidental.

 

I, for one, cannot wait to pan flush my 722.6 but it's been only 18-20K miles.

After every pan-flush, my car always drives better, shifting so smooth and no idle vibration.

 

I had a full flush/filter including torque converter at 44000 miles, and then took the car on a 1500 mile ride across N.A. Have another 500 miles on the 7 speed W209 CLK and now the transmission will not shift out of 1st gear and the CEL is on. Shift into R or D is a rough slam into gear, what happened?? Rodney, Glynn, thought I was doing the right thing?

 

Get the codes checked - it likely has nothing to do with the transmission service (unless it was done improperly). My guess is a bad speed sensor, which would fail regardless of the fluid/filter change.

 

+1^ ~ The transmission is in limp mode. As Rudeney says very likely a conductor plate/speed sensor implausible issue. This has zero to do with a fluid change. Unfortunately 2006 was the trouble year for 722.9 transmissions.

 

Took to Coral Springs dealer. Need valve body,being replaced under after market extended warranty, thanks Rodney and Glynn!

 

Good news. Unfortunately yours was a trouble year. Now you will have the latest VB & Conductor plate.

Also. While they are about it make absolutely sure that they replace the pan & spill tube with the latest articles.

 

I'm really pleased we have this thread. This is a classic example of a known early 722.9 failure for known reasons that could easily have been erroneously blamed on a fluid change.



Newer 722.9 transmissions do not require you to change the entire valvebody.

All you have to do is change the full conductor plate unit & flash the valve body calibration data from the old unit to the new TCU. Each valve body is flow benched.

 

I am glad this thread is here. I just purchased a new conductor plate Indy will be installing it on Monday The car just got worse in worse over the months going into Limp mode you can reset it so much. I never really noticed because I drive the car once a week.

 

We are pleased to have Rodney and Glyn, thanks for all your support and intelligence/experience. Makes this car a little more fun to work on.