Donald_from_OZ

SunnyRayToronto

- Did it happen before the service or only after
- Where did you get it serviced - Stealership - Indy - regular shop - or you did it yourself
- Which transmission oil used
- How did they measure amount
- Did they also check for leaking pilot bushing adapter

Supposed to get partial transmission oil change every 60K km,... was previous transmission service ever done

Donald_from_OZ

- Did it happen before the service or only after
>> Was happening before, that's why I had it serviced

- Where did you get it serviced - Stealership - Indy - regular shop - or you did it yourself
>>Independent Mercedes specialist

- Which transmission oil used
>>Authentic MB

- How did they measure amount
>>Not sure

- Did they also check for leaking pilot bushing adapter
>>Replaced O-Ring on a pluggy thing, its that it?

Supposed to get partial transmission oil change every 60K km,... was previous transmission service ever done
>>Probably not as local MB dealer don't push trans service.

SunnyRayToronto

Assuming they used the correct MB transmission fluid and put in the correct amount, I would suggest checking the Transmission Control Unit,.... pull the front passenger carpet at kickplate,.... and see if there is any trace of transmission oil at the Transmission Control Unit. If so clean with CRC QD Electronic cleaner.

Yes, pilot bushing adapter is that pluggy thing with o-rings,.... now they usually replace the whole pilot bushing adapter instead of just the o-rings.

Did they do a partial or full transmission oil change - how many liters of transmission oil were you billed for

Did they hook up the car to Mercedes-Benz STAR Diagnostic System - any error codes found
If they cleared the error codes - your car needs about 50km to adapt to your driving style

Glyn M Ruck

The transmission should hold gears for longer when cold until the cars warms up. Designed to heat the Cats more quickly.

Do what SRT has said. If this is the first change the transmission has had I would do another half change to get more of the old fluid out or flush.

Ask the dealer to reflash the TCU.
Good luck!

Glyn M Ruck

Flush procedure is here if needed.

https://mbworld.org/forums/c-class-w...sues-help.html

Donald_from_OZ

Drove the car into work this morning and it was 5 degress Celsius.
Clunky change was more pronounced until I drove about 3 km.
I appreciate the comments thus far but can anyone explain why it would be happening. What is the correlation between level and temperature, if the TCU unit was affected by oil why would it only do it when cold. If it is dirty oil why is it affected by temperature.
With the change up it seems like something isn't holding pressure or am I thinking old technology.

SunnyRayToronto

Donald,.... did you check the TCU yet,.... any traces of oil at all? It should not take more than 5 minutes to do. How many liters of transmission oil did they change? Then report back.

Why does your transmission clunky when cold and not when hot,... could be a number of items,... lets try to examine the more common and inexpensive items first and eliminate those variables before we go deeper into the more expensive fixes.

Transmission oil expands when its hot and it also flows better,... as it expands and flows better it reaches more area. Maybe you do NOT have the proper level of transmission oil in there - did you measure it at 80 degree celsius with a transmission dipstick? Yes, your indy did it,.... was this a Mercedes-Benz indy? BTW, I think your indy did a short cut fix on the pilot bushing adapter. You can NOT just buy the o-ring for the last few years; so unless your indy has been hoarding pilot bushing adapter o-rings, your indy used a non-genuine Mercedes-Benz part at a critical point. The entire pilot bushing adapter has been updated a number of times, it is a $12 part (MB part# A203-540-02-53). Yes, I am being so picky about this damn o-ring because it is a well known trouble point on 5-speed 722.6 transmissions. You must also ensure all the leaked transmission oil has been clean out of both the male and female plug, especially the female plug. It would be a good idea to double check your transmission oil level,.... go back to your indy or buy a clone mercedes 722.6 transmission oil dipstick off ebay ($20-25 shipped!) and measure at 80C.

Anyways,.... next time you start the car,.. put navigate the instrument cluster to coolant temperature display. Yes, I know we are focusing on your transmission problem,... but since we do not have a transmission oil temperature display and the transmission bone is connected to the engine bone which is connected to the coolant bone,.... this bonehead thinks the coolant temperature correlates and give an rough estimate of the transmission oil temperature. Anyways,.... instead of telling us how many km until transmission start shifting smoothly,.... tell us at what coolant temperature (roughly transmission temperature) the transmission starts to shift smoothly.

Then report back.

Donald_from_OZ

Thanks for the feedback, I am a technical writer by trade and can't help myself asking questions, I'm not doubting you, i'm just trying to understand the black art of MB transmissions. After you mentioned replacing the whole plug I realised he did as he showed me the old one, he mentioned the O rings were faulty and it was genuine MB as it cost $35 (we are in Australia).
Will check your suggestions.

leonardsigne

The transmission should hold gears for longer when cold until the cars warms up.

Glyn M Ruck

The first to second one way clutch might be damaged but the friction modifiers wear out in the transmission fluid. New fluid should smooth the change out. The friction modifiers in the fluid allow controlled slip of the clutch packs. If something was not holding pressure you would suffer clutch flare at the change.

Nothing should be done without checking fluid level that rises substantially with temperature & reflashing new software onto the TCU & setting all change adaptions. If this does not fix things then it's likely a repair required.

The 722.6 transmission is tough as hell & will do a million Km's if serviced every 60K Km's. The C200 engine does not stress it. It produces very little torque.

Please read & post transmission codes.

We need to understand why the transmission is not holding gears for longer when cold. Hopefully a software flash will fix this.

Donald_from_OZ

My Indy mechanic has reset the trans, there are no error codes and have followed Sunny's instructions. Mechanic has had 2nd opinion who think its the megatronic? board. If the trans is supposed to hold in gear whilst cold how does the trans know when it is warmed up?
Mechanic is investigating that aspect before any major surgery.

Btw the thermostat was faulty and he car is warming up quicker.

Glyn M Ruck

It knows the temperature of the engine from the ECU - change is engine temperature controlled.

How did he reset the transmission? Does he have a Star?

First change the oil & filter. Then have all transmission adaptions reset with Star. If that does not work then reflash the TCU. If they can't get all adaptions within spec then they will know exactly where the problem lies. i.e which clutch pack or area of the valve body is playing up.

The only "board" in the transmission is the conductor plate mounted to the valve body that the external TCU plugs into via the electrohydraulic pilot bush on the front diagonal RHS of the transmission. The TCU is mounted in the car under the passenger kick plate. A harness connects it to the transmission.

If the conductor plate is damaged you will have stored codes. The most common of which relate to solenoid valves & speed sensor data being implausible.

Donald_from_OZ

Have followed all instructions so far
Changed oil 3 times
Changed conductor plate
Renewed plug, there is no oil in TCU
There are no error codes
Adaption has been done.
Oil level is within tolerance

When car is warm it runs fine.
For first 2 kms when you come to a halt it seems that the car hasn't changed down a gear to match speed and car shudders as you stop. When its warm its OK.

Could this be:
solenoids
valve body
clutch packs
Faulty conductor plate?

Despite being changed 3 times the oil isn't pristine.

Any suggestions, If I had hair I would pull it out.