Had my transmission fluid serviced last week, Mercedes was running a special for $279.

While there, I asked them about an issue I was having when on the highway and making turns how my car would hesitate after I hit the accelerator. In other words, I would take my foot off the gas into a turn and then accelerate out of the turn. When doing this, my car couldn't make up its mind what gear it wanted and would hesitate. Same for when passing on the highway.

They drove it, said they saw the hesitation and said I needed the updated TCM(Transmission Control Module) software for the transmission. Well not sure what they did, but my shift pattern is different and seems like the car is shifting far too early, it shifts hard between 2-3-4-5 and the hesitation is not better, maybe even worse. Taking it back tomorrow.

Does the new TCM change the shift points? Just curious if anyone had any thoughts on what they did or any experience like this. Thanks

Joe.

 

What mileage did u get ur trans fluid done at?

 

60k

 

Is that kilometers or miles? The first change was/is due at 39000 miles.

 

Miles.

 

It should not shift harder or hesitate. Regarding the holding of gears. This is an adaptive transmission that learns your driving style which is obviously moderate. When they reflash the memory is lost & it will take a while to relearn your driving style.

 

Exactly what they told me today. He said a week wasn't long enough and to give it a few more. He also said the hesitation I refer to is when I am giving it too much gas and it needs to calculate which gear it wants, typical when passing on the highway. He also said the gear shifting is fine and that its the new shift points I feel. He said to drive it for a couple more weeks and it should adapt more to my driving style. He also said 60k miles was fine for transmission oil change would not cause any of the issues in his opinion. He said what I am feeling now is the new tcu flash.

Sounds good to me.

 

Let's hope that 60K trans fluid change OK'd by somebody at the dealer is in writing because if the trans develops a problem later because you didn't follow the MB fluid/filter change recommendation that they then decide caused the problem, you will have no recourse.

 

60K is not wise with this transmission.

 

I agree Glyn, not wise. It was my fault for missing it. They reminded me when i put tires on last month that it hadn't been done. Its still shifting harder between 2nd to 3rd to 4th to 5th but I haven't even driven 200 miles yet so we will see if it adapts or gets better. Probably not used to the viscosity of new oil. If it gets worse, well, I would be to blame for waiting too long and I guess at that point I will figure out what to do next.

 

I'm not so sure the late transmission oil change has much to do with what you're describing as "harder shifting" (especially if it was doing it BEFORE the tranny service and is still doing it AFTER).

That said, it is my understanding is that the TCM dealer update/flash is only designed to handle the hesitation some C's have experienced when shifting between reverse gear and first gear (and vice versa). Which is quite different than a TCU reset that is intended to return the shift points to factory settings, after which you can then re-establish those points via the adaptive control system.

I can tell you that for the first couple of months I had my C, I would get pretty irritated when it would sometimes down shift two gears at once, which made passing and/or sudden acceleration a bit of a chore and maybe even an embarrassment at times.

My frustration became worse when I would reset the TCU (no "dealer flash" needed/you can reset it yourself/see below), go out there and immediately try to force it to re-learn my somewhat spirited driving style (as some people have suggested in various threads).

IMHO, it is better to understand that "adaptive" does not mean "immediate"; it is an ongoing process that will take a few weeks. So rather than trying to immediately under-estimate/over-compensate for what the car can do on its own over a short period, you should ease your way into your normal spirited driving style. In other words, you should allow it to learn your preferences all while you're also learning about its capabilities and adjusting your driving style accordingly.

I can tell you that for me, that has worked much better in that it has been a while since I've gone through a reset... And the shifting "problems" (if I can describe them as such) are long gone.

Anyway, to reset the TCU, you follow this simple procedure:

Steps to Reset the TCU:

Resetting the TCU will reset transmission to factory shift points and the car will 'relearn' your driving style.

(1.) Turn the ignition key to the on (not start) position (dash lights on/engine not running).
(2.) Press the gas pedal to the floor and hold for five seconds.
(3.) Turn the key to the "off" position (don't remove the key), then release the gas pedal.
(4.) Wait at least two minutes for TCU to reset.

* For step #2, there are some who would suggest only stepping on the pedal to the halfway point (see this thread). Personally, I can't say that it did much for me that way, but you're free to try.

 

My car used to shift much smoother before service. In fact it shifted like butter. I did the change because I hadn't done it yet and it needed to be done. I told them exactly where my hesitations were and they have not changed since they did TCU flash. Still hesitates when coming out of a turn/accelerating and still when trying to pass on the highway.

Basically my car still has the hesitation problem and now has a new problem which is harder/rougher shifting between those gears mentioned above.

I will drive it for a few hundred miles and if it doesn't get better I will take it back again. I am skeptical, but I'm not a mechanic.

 

Double downshifts are absolutely normal for this transmission and it's five speed predecessor. My 2001 C320 did this also but it didn't take me long to realize it was normal as long as the engine wouldn't be overrevved. Try flooring it at 40mph and see how far down it shifts.

 

I bought a my c320 cdi with the 7g tronic and it is recomended to change the tranny oil at 50000km how ever my car is on 65000 i am doing the oil change this weekend, Is this bad? Can this harm my tranny? It wasent my fault when i bought the car the dealer said that it was fully serviced..
>_<

 

No - you will be fine. Benz recommendation is generally every 60,000Km.

 

Please note: Benz knows that they have had speed sensor & valve body (electrohydraulic unit) issues on some 722.9 transmissions requiring replacement. Yours might be one of these. Benz must pay if it is.

 

My bad... I misread your original post thinking you had both the hard shifting AND the hesitation at the same time, and that you discussed it with the dealer at the time you had the transmission fluid service...

Still, I would try and reset the TCU myself to see what difference, if any, it will make.

Good luck, and keep us updated!

 

Well I hope that is not an issue but if it is, i will post here.

I checked my bill, it says the following for transmission service:

QTY --- FP -- NUMBER --------------DESCRIPTION
1 PK7229 TRANS SERVICE
1 221-277-01-95 Oil Filter
2 04113 4QT SYN ATF
1 220-271-03-80 Gasket
1 007603-012102 Ring.General

So it appears they used 8 qts of fluid or at least they charged me for 8 qts.

For the Software upgrade it reads this:

PERF ETC SOFTWARE UPDATE AND ADAPTATIONS

As for resetting the TCU on my own, I'm not going to do that. I don't want to introduce any other variables yet. I have some traveling to do this week so we will see if it gets better.

 

They have done everything they should including the TC drain. Agree just drive it - Don't introduce more variables or you will never diagnose the problem.

Karo on the 203 forum had to have a new ECM on his 350 fairly recently. It can only be replaced as a complete assembly. Benz paid IIRC. He was also overdue on his service but they still paid out. It is not a fluid related problem.

Forewarned is forearmed with dealers if they try & tell you something is normal & you know how smooth your tranny used to be. They think we are all stupid.

722.9 transmission









This is one of the potential problems. There are others with the conductor plate etc.



Good luck

EDIT: One final thing. Make sure they used the correct fluid meeting 236.14. I'm pretty sure they did. It's an unlikely mistake by a dealer but a forlorn hope.

 

Wow!

Great post Glyn. Thanks

 

Thanks Kevin. If the software is correct & the fluid is correct (type & level) and the adaptions have been done correctly with Star - the next suspect is always the speed sensors as long as there is no mechanical damage.

If speed sensor inputs are off or non existent the electronics are unable to adapt for smooth range transition from one gear to another resulting in harsh changes. Y3/8n2 failure is frequently the cause.

 

Glyn, thanks for the pics. Went to the dealership again today and discussed the trouble with one of their mechanics. Had to make an appointment to drop it off monday evening so they can have it cold Tuesday morning. Tech said he first wants to check fluid level(which has to be done cold). Next he wants to set the adaptations again. I will let you know how it works out.

As for all this other stuff you mentioned, the sensor, the electrohydraulic unit. I will keep that in mind if it doesnt get fixed.

Do you know if there is a way to set the adaptations back to what they were before my service? Since it shifted better before they performed adaptions and TC flash, why not revert back?

And what did you mean when you said "benz paid IIRC" ?

 

They can reflash with older versions of the software. It does not really make sense to do so however.

MBUSA paid for the electrohydraulic control unit & labour on Karo's car.

 

Glyn, my car today got 9 bottles of 001-989-68-03-13 transmission oil. Do you think that is the current oil? Car feels smoother and a bit more responsive. Might be in my head, but better than the other way around.

Would 9 bottles be all they would have needed if they got ALL of the old fluid out including torque converter?

They also did gasket, oil filter, a ring, and some screws and screw plug.

 

Hi mac - yes they have done a complete change at 9 quarts/litres.

Your fluid is correct. The number above was the launch parts code in a 1 litre pack from Europe - 236.10 - now upgraded to 236.14. Numbers vary on source & pack. (Sorry - I should have updated the training slide - I was thinking speed sensors not fluid!)

236.10 = A 001 989 21 03 10
236.11 = A 001 989 22 03
236.12 = A 001 989 45 03 13
236.13 = A 001 989 23 03
236.14 = A 001 989 68 03

I find all Benz autos feel good after a fluid change & replenishment of friction modifiers.