722.9 7-speed transmission problem. - Page 3 - Mercedes-Benz Forum

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post #21 of 87 (permalink) Old 03-18-2010, 04:49 AM
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That sounds bad
Sorry to be the one to hit you with the bottom line but that is where it normally ends up and MB are not stupid as they will not sell the control module seperate from the valve body which makes it expensive.

We have changed many here in China and even with a new unit fitted, adaptations are a real pain to finish correctly.

ERIC.

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post #22 of 87 (permalink) Old 03-18-2010, 02:09 PM Thread Starter
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Originally Posted by eric242340 View Post
Sorry to be the one to hit you with the bottom line but that is where it normally ends up and MB are not stupid as they will not sell the control module seperate from the valve body which makes it expensive.

We have changed many here in China and even with a new unit fitted, adaptations are a real pain to finish correctly.
There is many thanks to you and all others providing important information.

I do hope MB can make their product better in quality. What else can I say?
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post #23 of 87 (permalink) Old 04-05-2010, 08:29 AM Thread Starter
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Being busy for the past couple weeks so there is no time for me to have the problem fixed.

Is it possible the transmission is overfilled instead of underfilled? The fact the problem only happening after stopping the car for a while sounds to me more like it is a overfilled problem. After a short stop (say 15 minutes), the transmission is still hot and all the fluid drains back into the pan, and these make the fluid level in its highest inside the transmission. Once the car starts again, if it is mainly driven locally, it may not have a chance to shift to the higher gears, which leaves relatively more fluid in the pan comparing to highway driving. If the tranny is overfilled, the high fluid level may cause foaming of the fluid to make it overheat. Unfortunatly, the producedure of checking the fluid level with 722.9 only tells if it is underfilled, but cannot tell if it is overfilled. I am going to the dealer to ask them refill the fluid and do it carefully not overfill it to see what heppen later.
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post #24 of 87 (permalink) Old 04-05-2010, 08:35 AM
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Being busy for the past couple weeks so there is no time for me to have the problem fixed.

Is it possible the transmission is overfilled instead of underfilled? The fact the problem only happening after stopping the car for a while sounds to me more like it is a overfilled problem. After a short stop (say 15 minutes), the transmission is still hot and all the fluid drains back into the pan, and these make the fluid level in its highest inside the transmission. Once the car starts again, if it is mainly driven locally, it may not have a chance to shift to the higher gears, which leaves relatively more fluid in the pan comparing to highway driving. If the tranny is overfilled, the high fluid level may cause foaming of the fluid to make it overheat. Unfortunatly, the producedure of checking the fluid level with 722.9 only tells if it is underfilled, but cannot tell if it is overfilled. I am going to the dealer to ask them refill the fluid and do it carefully not overfill it to see what heppen later.
You are grasping at straws here, the problems are with control and not fluid.

ERIC.

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post #25 of 87 (permalink) Old 04-07-2010, 01:32 PM Thread Starter
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You are grasping at straws here, the problems are with control and not fluid.
Just came back from the dealer, and they confirmed the problem is the input sensor in the valve body as P0717 stands for. It happened 12 times in total from the TCM log.

I read somewhere the speed sensor is an optical sensor and its window is easily contaminted by the Graphite deposite used inside the tranny. Also, if the fluid is with too much of the Graphite, it can make the sensor fail intermittently. With this in mind, is it worth having the fuild flushed once and the sensor cleaned before having a new valve body. It is only $300 to flush the tranny compaing to $1700 to have the valve boday reaplaced. I know most repair for this kind of problem is done with replacing the valve body, but wonder expecially for the 722.9, if the cleaning and flushing work?
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post #26 of 87 (permalink) Old 04-07-2010, 10:07 PM
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^Hate to put you off on this but if you change the fluid you will still need a new valve body, I speak from vast experience on these transmissions and the valve body/control module are the culprits. Sorry to say.

ERIC.

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post #27 of 87 (permalink) Old 04-08-2010, 08:47 AM Thread Starter
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^Hate to put you off on this but if you change the fluid you will still need a new valve body, I speak from vast experience on these transmissions and the valve body/control module are the culprits. Sorry to say.
Hear you, Eric. Thaks.

My car is in the dealer to have the valve body replaced.

What do I need to do to make my NEW valve body last longer other than change ATF regularly with a known good MB mechanic (which I did in a dealer previously)?

Try to see if MB and the dealer can take it under warranty because the record in the TCU clearly states that the first occurance of the problem is at the milage bellow 50K. They both said "NO". what a .....

Also, as a note, the dealer put into the part list of 10 liters of ATF, but there is not indication that the torgue converter needs to be flushed. I have to make sure with the forman that has to be done. By doing this, I can see the impatient face of the SA.

This is the first car I own that requires a major tranny work in only a bit more than 3 years.
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post #28 of 87 (permalink) Old 04-08-2010, 08:59 AM
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^It is a known problem with these transmissions but does not affect them all so no recall. Most of the failures are just out of warranty - bummer is it not. Good news is once a replacement has been done they do not seem to fail.

It is important they do the adaptations correctly after the replacement or you may find teething problems with it.

ERIC.

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post #29 of 87 (permalink) Old 04-08-2010, 09:34 AM
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The valve body and electronic module seems to not be the final solution to some of these, either. My valve body and electronic module were replaced in January. The slamming into 1st. symptom after complete stop is still continuing. I've found this symptom can only be corrected by replacing the B2-B3 linkage, whatever that means. In any case, the linkage gets damaged from the constant malfunctions the tranny experiences when the valve body and control module goes bad. As eric has patiently pointed out to you, the flush at 39,000 miles was designed to eliminate the graphite contaminated fluid that caused this issue to begin with. So, continuing to change fluid is not going to correct your problem and I think your tranny is doomed to have the same issue even after the valve body and control module are replaced. So, I'm saying that the 39,000 mile flush is too little, too late as my vehicle is headed back to the dealer for more tranny repairs.
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post #30 of 87 (permalink) Old 04-08-2010, 09:46 AM
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The valve body and electronic module seems to not be the final solution to some of these, either. My valve body and electronic module were replaced in January. The slamming into 1st. symptom after complete stop is still continuing. I've found this symptom can only be corrected by replacing the B2-B3 linkage, whatever that means. In any case, the linkage gets damaged from the constant malfunctions the tranny experiences when the valve body and control module goes bad. As eric has patiently pointed out to you, the flush at 39,000 miles was designed to eliminate the graphite contaminated fluid that caused this issue to begin with. So, continuing to change fluid is not going to correct your problem and I think your tranny is doomed to have the same issue even after the valve body and control module are replaced. So, I'm saying that the 39,000 mile flush is too little, too late as my vehicle is headed back to the dealer for more tranny repairs.
Unfortunately this can happen, when the module/valve body go wrong, internal transmission damage can occur and I am as guilty as the next tech of overlooking this or trying to avoid it. But it is rare and maybe one in twenty go this route.

ERIC.

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- George Bernard Shaw to Winston Churchill.

"Cannot possibly attend first night, will attend second ... if there is one."
- Winston Churchill, in response.
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