I have a 2004 C240 100k miles.
My symptoms are very similar to the valeo radiator leak, but I have a behr radiator.
When shifting normally in lower gears it will buck and then make a noise that sounds like driving on the rumble strips on the side of the road. it has harsher shifts in higher gears and sometimes downshifting, but nothing as dramatic as 1>2 and 2>3. If steady the car at about 1500 RPM the rumble strip noise once started will continue until I get out of that RPM range.

Here is the thing that is perplexing to me. So far this has happened 3 times, each time I am able to go to a mechanic have them reset the torque converter lockup adaptations, it will drive perfectly for approximately 10 days and then the same exact symptoms will return.

Any ideas? I am on the cusp of just selling the car if I can't find any solutions, I am not about to throw money at the problem.

 

have you changed the transmission oil?

 

Yes I drained and refilled it twice, I bought the car with 90k miles, this was about 5k miles before the issues started happening. changed the filter the leaky TCU plug, One thing I did notice is someone had already accessed the TCU under the passenger floorboard, so I assume there was some issue previously.

 

Please check that the transmission tailshaft flange nut has not come loose (happens from time to time). Also check rear transmission mounting. Propshaft flex discs & centre hanger bearing.

 

Would one of these issues be consistent with an issue that goes away when the torque converter is reset? to me I highly feel it is an electrical/computer issue, because it shifts perfectly for about 500 miles after resetting torque converter lockup.

 

do you see any signs of oil leak under the passenger carpet it could be the computer?

 

Ever see metal flakes in your pan during your flushes? From what I read you have a serious issue that should be looked at by a mercedes technician.

Possibilities from cheapest to most expensive:
Torque converter solenoid
Conductor plate
Valve body blocked passage
Transmission mechanical failure

 

Yes ~ it could & is likely an internal issue but these are easilly checked external items. If readaption gives smoother torque delivery at the tailshaft it can sometimes mask trouble in these areas.

A doctor friend in Cape Town recently had a W211 E Class in and out of the dealership numerous times with a problem similar to yours. Finally the dealer said you need a new transmission. We put it up on a hoist & found the tailshaft flange nut to be loose. Tightened & relocked it. Problem gone.

What codes is the transmission showing?

 

There have never been any codes.

No oil under floorboard at TCU, However, I did notice the TCU had been accessed before, so there was obviously a problem with a previous owner. there was a tiny bit of oil in the conductor plate connector plug that I changed about 5k miles ago, it was such a small amount that it could have been left over from the original change.

Yes when I dropped the pan about 5k miles before the issue started there was 10-15 shiny metal flakes.

I spoke to a few mechanics and basically I am going to have to wait until it starts acting up again and then have someone look at it.

 

Sadly shiney metal flakes can be misleading. Benz QC was so bad at one time that some transmissions had original machining swarf in them.

Some images from my hall of horrors. This transmission is still operating normally many years later.

 

The fix is to get the transmission re-adapted with a STAR, which it sounds like you may have already done. Mine did exactly that for about a day and had almost exactly the same miles as yours. Strange 1-2 and 2-3 shifts and occasional weird sounds.

I didn't try to reset the transmission the free way which apparently is as follows: (radio, everything off.....turn ignition key to position II.....push accelerator to floor far enough to turn on floor switch.....hold pedal down for 15 seconds......while holding pedal down, turn key to position I.....let up on the accel pedal.....do nothing including not opening door for a minute.....remove key.....start car); Once reset, drive VERY slowly from first to second gear and then coast until definite shift back to 1st....do this several times.....do the same for 2nd to 3rd and back down (slowly).....eventually do that for all the gear shifts then while on the highway do several final gear to passing gear and back down.....after all this, just cruise around slowly for about 15-20 minutes).

I do most of my own work, but I have a MB place close to where I work, and so decided to have them look into it so I would have a bigger picture (STAR diagnosis) from which to make a decision. I had just had the car aligned at an indie the day before and told them that I suspected that something had accidentally gotten reset. I had had absolutely no transmission issues whatsoever before the alignment. MB called later and said that they reset the electronic tranny module and that it seemed to take the re-adaptation so that everything should be good (which its been so far) but that if it went back to acting weird again that the module ($1200 as I recall) likely needed replacing...which unfortunately sounds like what you might be heading towards. At least access to the module is very quick and easy although any new module has to be programmed on the vehicle by MB. Good luck.

 

That process is a throttle reset. All it does is realign the throttle plate with the pedal. i.e foot on the floor = WOT

 

Thanks Glyn. That's good to know. There have been threads galore on various sites claiming that that is the way to reset the tranny module. Makes sense though that it's throttle position related. I do know that the routine I've given for re-teaching the adaptation, once reset, is one of the two correct ways described in the diagnostic documents for the 722.6. Thanks for debunking the accel pedal tranny reset myth though.

 

You said it seemed to take the re-adaptation, and a process for re-teaching adaptation? I have seen a few things about doing this properly, I am wondering if that is where I could be going wrong, as I am having it reset and then just driving off.
Also, mine was not re-adapted with STAR, the mechanic had another system and he reset the torque converter lockup, so I wonder if I should look into having it done "properly" with a STAR?

As far as the TCU, is there anything additional that I could have done in it's regards, such as flashing the TCU firmware? You mentioned re-programming a new one, can I re-program my old one? I know people sell them used so maybe there mine got messed up along the way and needs to be flashed, As I mentioned before, the TCU had been accessed prior to my troubles by a previous owner, But it drove fine for 5k+ miles after purchase.

However, when I was doing maintenance, changing the leaky transmission plug I did forget to plug it in and it limped the car, I took it to my indie and he cleared the codes (not sure if he reset anything). But it fixed that issue so maybe that has something to do with it.

 

So its been a week since I reset the torque converter adaptations, two things I have noticed this time driving the car, when I first start driving and get to 30-50 MPH it makes like a pulsing very slight vibration, it will go basically constantly till the car warms up, might not have anything to do with transmission.

Also, about 2 seconds after shifting from 2>3 I will feel a slight bump, a very slight rpm drop or just a shake on the needle and following that a very faint rumble. This would be in line with what happens when the problem is full blown, but much less severe, it is completely driveable and probably wouldn't notice it unless I was trying to. Although I expect it to become worse gradually the more I drive.

 

That very slight bump you are detecting might well be the TC clutch locking the converter.

For the transmission one should really check every clutch pack lock up is in spec & readapt if necessay & possible with a Star.

Check the rear tranny mounting & propshaft flex discs etc for trouble.

 

I will try to check the mount and flex discs.

Once it gets bad I do plan to take it to a shop with STAR and hopefully it just has something to do with them not re-adapting properly.

 

Is this what I would need to have done for adaptation?:

Remedy
There are 2 steps for adapting the torque converter lockup clutch:
1. Adaptation via coolant temperature and
2. Adaptation in 3 torque windows.

1st Step, adaptation via coolant temperature:
1. Perform cold start
2. Engage gear range "D"
3. Move steering wheel to straight-ahead position and brake vehicle for 20 seconds with service brake
4. Drive until coolant temperature has increased by approx. 20°C (at least 18°C but not more than 22°C)
5. Repeat steps 3 +4 until the operating temperature (coolant temperature) of 80-90 °C is reached.

2nd step, adaptation in 3 torque windows:
1. Transmission oil temperature must be over 60 °C
2. Gears 2-4 are best suited for the following steps (if necessary limit the transmission to these gears with the gearshift lever) as is driving on a level road surface at a speed between 40 and
80 km/h.
3. Drive vehicle to torque range of 20 - 40 Nm (rpm between 1200 and 1500 rpm) and hold for at least 5 seconds (menu
of upshift 2-3 is suitable for display). If it was not possible to maintain the torque range for 5 seconds, repeat this step.
4. Drive vehicle to torque range of 40 - 80 Nm (rpm between 1200 and 1600 rpm) and hold for at least 5 seconds (menu
of upshift 4-5 is suitable for display). If it was not possible to maintain the torque range for 5 seconds, repeat this step.
5. Drive vehicle to torque range of 80 - 120 Nm (rpm between 1500 and 1800 rpm) and hold for at least 5 seconds (menu
of upshift 4-5 is suitable for display). If it was not possible to maintain the torque range for 5 seconds, repeat this step.
6. After termination of the adaptation procedure, always leave the engine running with vehicle at standstill for approx. 10 minutes. This is
necessary so that all values are transferred to the control unit memory without exception

 

Where is this flange nut located under the car? I'd like to check mine and see if it alleviates my issues.

 

Remove the propshaft from the transmission flange & it will expose the nut

 

Hmmm I will bring this up to the indy that works on my car soon when I take it in for new brakes and rear control arm bushings. That occasional hard shift annoys me and the transmission flush and fill did help quite a bit. The occasional hard shift and rear area clunk make me think that there's still something else going on and before I decide to pull the trigger and pay $975 for a new conductor plate I need some more info.

 

I just recently started getting the rumble strip issue but it is only noticeable when the car is cold. Once it warms up, it goes away. It's odd, to say the least. I'm wondering if maybe I have the Valeo radiator...

 

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