722.6 cold lurching and harsh shifting

[mickael]

i have been reading some postings with somewhat similar issues with interest.but my problem seems somewhat different so thought i would start a new thread. i have a 2005 e320 cdi and when the trans temp is cold and the ambient is below 50F, i have harsh shifting in all gears and it seems to want to upshift way too soon. this results in the car lurching down the road and sometimes the engine will hunt up and down about 100 rpms. especially in 3rd gear. trans fluid and filter changed regularly at 25-30,000mi and most recent was about 4000 mi ago. using pentosin atf-1 in it. have about 300,000mi on the vehicle. no codes. once the temp is up the trans operates normally with an occasional brief down shift when at highway speed. this has only happened a few times. i have also experienced the lurching problem even when the electric engine heater has been on and engine at 80c but trans is not up to temp. i have read on some of the postings about a temperature sensor inside the trans, where is that located? anyone have any new ideas on this issue?
thanks
mick

 

[Arudge]

i have been reading some postings with somewhat similar issues with interest.but my problem seems somewhat different so thought i would start a new thread. i have a 2005 e320 cdi and when the trans temp is cold and the ambient is below 50F, i have harsh shifting in all gears and it seems to want to upshift way too soon. this results in the car lurching down the road and sometimes the engine will hunt up and down about 100 rpms. especially in 3rd gear. trans fluid and filter changed regularly at 25-30,000mi and most recent was about 4000 mi ago. using pentosin atf-1 in it. have about 300,000mi on the vehicle. no codes. once the temp is up the trans operates normally with an occasional brief down shift when at highway speed. this has only happened a few times. i have also experienced the lurching problem even when the electric engine heater has been on and engine at 80c but trans is not up to temp. i have read on some of the postings about a temperature sensor inside the trans, where is that located? anyone have any new ideas on this issue?
thanks
mick

What are you using to read the codes? At lot of generic code readers won't read MB transmissions. You really need STAR for this one.

 

[mickael]

using an

What are you using to read the codes? At lot of generic code readers won't read MB transmissions. You really need STAR for this one.

icarsoft mbII reader. it isnt a star but it reads most of the codes, albeit a bit slowly

 

[alexanderfoti]

Probably an issue with the tc. It's most likely worn out at 300,000 miles, but you can send the valve body off to be checked before doing that.

This is assuming you have checked the common things like:

Fluid level (critical)
Fluid type (234.0)
Adaptions are not off the top of the scale on any of the clutches or brakes (need star to read these, don't think Icarsoft will show adaption values).

 

[Arudge]

You have probably read my own posts about transmission issues and i ended up replacing the transmission.

I also had lurching but different to yours, on inspection I found a failed sprag bearing. That transmission had done just 105,000 miles.

I'm not sure what transmission you have. No codes suggests a mechanical failure possibly similar to mine, I also had no codes.

The temperature sensor on mine is mounted on the electro plate which is within the body of the transmission, but reasonably easy to get at. The gearsets are not accessible and require a full strip.

 

[Arudge]

don't think Icarsoft will show adaption values).

I have Carsoft which similar but PC based, Neither will read adaptions.

 

[Steve@Avantgarde]

I would say it’s a TC lock up valve issue together with poor fluid quality.

 

[mickael]

I would say it’s a TC lock up valve issue together with poor fluid quality.

i was thinking the same on the valve,though it seems odd to do it only when cold. as for the fluid quality, only about 4k miles on it....is like new.

 

[mickael]

You have probably read my own posts about transmission issues and i ended up replacing the transmission.

I also had lurching but different to yours, on inspection I found a failed sprag bearing. That transmission had done just 105,000 miles.

I'm not sure what transmission you have. No codes suggests a mechanical failure possibly similar to mine, I also had no codes.

The temperature sensor on mine is mounted on the electro plate which is within the body of the transmission, but reasonably easy to get at. The gearsets are not accessible and require a full strip.

 

[mickael]

i dont know enough about how the tcu operates, but the temperature sensor may be telling it that the oil is up to temp and shift sooner than it would if cold. i dont think a bearing would cure itself when it warmed,though perhaps a valve or solenoid could.....though it would seem it would need to be at full operating temp before that would have an affect. but that is just my gut feeling

 

[Arudge]

i dont know enough about how the tcu operates, but the temperature sensor may be telling it that the oil is up to temp and shift sooner than it would if cold. i dont think a bearing would cure itself when it warmed,though perhaps a valve or solenoid could.....though it would seem it would need to be at full operating temp before that would have an affect. but that is just my gut feeling

This is a sprag bearing, they only rotate in one direction and lock in the other, it a least there supposed to. There are two sprag bearings and they are known to fail. When warm they will expand and are more likely to lock when they should, slip when there cold.

 

[Arudge]

These transmissions are fiendishly complicated. On mine you have 4 solenoid valve controlling 7 gears because the valves are shared, and there modulating valves as well, supplying different pressures on demand. If a valve is faulty on downshift it will be faulty on upshift also, it does both. The solenoid valves send oil to the spool valves which in turn send oil to the selected brake or clutch, or both depending on the criteria.

The TC stands out because it has its own valve and it's own circuit, there are also known issues with it locking on.

I don't think temperature is part of the criteria, the temperature sensor is there to set correct fluid level, that is all.

The valve block contains a lot of spool valves. It may be that the master control valve is leaking because it's worn, it's not hold enough pressure. I think there are 7 different pressures and none of them are monitered, if your losing pressure in any circuit then strange things happen.

The valve block can be tested but it needs to be removed and sent away.

 

[umblecumbuz]

These transmissions are fiendishly complicated. On mine you have 4 solenoid valve controlling 7 gears ....

I don't think temperature is part of the criteria, the temperature sensor is there to set correct fluid level, that is all.

The OP has the 5g box, not the 7g, so there may be slightly less complication.

Now that - the function of the temperature sensor - is something I've learnt today. I thought it had a more widespread function. Great things, forums!

 

[Arudge]

The OP has the 5g box, not the 7g, so there may be slightly less complication.

Now that - the function of the temperature sensor - is something I've learnt today. I thought it had a more widespread function. Great things, forums!

The 7 gears are 5 forward and 2 reverse. Mine is also 5g but I wasn't sure about the OP.

 

[Arudge]

The frustrating part of the valve block is that there are no test points to check pressure, they are generally tested with a vacuum device, one valve at a time. Similarly, the TCU sends instruction to a modulating valve but then assumes that, that has been actioned, there is no feedback to tell the TCU that the correct pressure has been achieved nor that the circuit is holding pressure. The TCU collects data from the speed sensors and if the drum is rotating at the correct speed then all is well. The TCU doesn't appear to "see" small glitches and only reports a fault when something has let go good and proper, by which time you've ground to a halt.

It's very, very clever.

Nightmare to diagnose.

 

[Steve@Avantgarde]

The valve chatters from cold and the TC lock up clutch is constantly engaging and disengaging which is why you get the surge and hunting revs if you try and hold a throttle position.

I fixed another forum members car a few weeks back that had the same issue which a fluid change did not cure.

 

[Steve@Avantgarde]

http://forums.mercedesclub.org.uk/index.php?threads/w203-c220-auto-box-issue-easy-change.164042/

This is the very thread!

 

[mickael]

The valve chatters from cold and the TC lock up clutch is constantly engaging and disengaging which is why you get the surge and hunting revs if you try and hold a throttle position.

I fixed another forum members car a few weeks back that had the same issue which a fluid change did not cure.

very interesting information. is the valve you replaced within the valve body?? or is this a solenoid on the conductor plate you are replacing? i know how to get the valve body out ok, is this something i can do myself?

 

[mickael]

These transmissions are fiendishly complicated. On mine you have 4 solenoid valve controlling 7 gears because the valves are shared, and there modulating valves as well, supplying different pressures on demand. If a valve is faulty on downshift it will be faulty on upshift also, it does both. The solenoid valves send oil to the spool valves which in turn send oil to the selected brake or clutch, or both depending on the criteria.

The TC stands out because it has its own valve and it's own circuit, there are also known issues with it locking on.

I don't think temperature is part of the criteria, the temperature sensor is there to set correct fluid level, that is all.

The valve block contains a lot of spool valves. It may be that the master control valve is leaking because it's worn, it's not hold enough pressure. I think there are 7 different pressures and none of them are monitered, if your losing pressure in any circuit then strange things happen.

The valve block can be tested but it needs to be removed and sent away.

interesting information.....especially on the temp sensor. seems kind of overkill to use a sensor for just level sensing

 

[Steve@Avantgarde]

Its a valve on the EHCU. You need to remove the EHCU from the car to replace it.