Transmission jerk on 5 speed auto - torque converter?

[Bobby Dazzler]

I've been reading up on a problem that seems to affect SLK32 and C32 AMG owners, although I suspect it affects other models too given the automatic gearbox is not unique to these models.

People describe a jerk at 1500rpm when accelerating gently - many confuse it for an abrupt gear change, but one MB Tech in the US discovered some time ago that it was the torque converter locking up. When he sent the signal to lock it, he could replicate it at any engine speed.

Apparently replacing the TCU (Transmission Control Unit) or re-flashing an existing TCU cures the problem.

Has anyone in the UK suffered with the symptoms, had the TCU re-flashed or found some other solution to the problem?

 

[mchips]

I just had this unit swapped out for a similar problem on my U.S. w202. I am not really sure that it will improve things. At first it seemed like things might have improved, but now it seems like it might be heading back to its old ways. I think they reset all the adaptions after the new control unit went in. Now it may finally have been driven enough to re-learn things and may be back up to its old behavior. I have not driven it much, so it is hard to say for sure at this point and today was a wet, cold, nasty day so maybe the car was just crabby. Luckily it was still under warranty, so I didn't worry about the upgrade. If I had been paying for it myself, I would have been much more cautious about the replacement!

 

[Rose Chap]

Interesting. I posted this last week highlighting an issue with my transmission. I've got a feeling mine might be more related to age/MAS/mileage than anything else though.

http://mbclub.co.uk/forums/showthread.php?t=33402

Mine is also a five speed auto however.

 

[Rory]

This is nothing to do with the glycol leak into the ATF, is it?

It's usually more of a judder than a jerk, but someone on another forum reported jerky 1st to 2nd and the found coolant in the ATF.

(Search for glycol in the forum).

 

[Bobby Dazzler]

Interesting. I posted this last week highlighting an issue with my transmission. I've got a feeling mine might be more related to age/MAS/mileage than anything else though.

I read your post before starting a thread. Although the symptoms are similar, it seems as though the conditions that lead to it are slightly different.

The jerk I mentioned only happens at or very close to 1500rpm - at least on the C32 - under very very light accleration from rest.

However it is often confused with a jerky gear change, and so may be a very similar to the problem you described.

 

[Bobby Dazzler]

This is nothing to do with the glycol leak into the ATF, is it?

It's usually more of a judder than a jerk, but someone on another forum reported jerky 1st to 2nd and the found coolant in the ATF.

I think these two issues manifest in similar ways, and it's difficult to really know the difference - one man's shudder is another man's jerk!!

However the torque converter locking issue seems to be a solitary jerk/thump at a very specific engine speed. The shudder - or jerks in quick succession - under a range of conditions seems to be more characteristic of Glycol contamination, as far as I'm aware.

I had a Glycol test a few months ago, and the result was OK, so I'm keeping fingers crossed it's not that.

 

[Dieselman]

I doubt the lock up clutch is locking at 1500 rpm, more likely the car is changing gear. Mine changes at 1500 on light throttle.

Drive the car and count the changes or after it has changed pull the stick to engage first and see if it changes back down, alternatively try the winter selection to see if it stops the jerk at the set road speed.

 

[timberman]

i've had this problem on mine for some time now.

it was present before the warranty ran out but every time i mentioned it to the dealer they showed little interest and tried to tell me this was quite normal. I did get them to do the glycol test and it came back negative.
I've also read that changing the tcu and or updating the software is a possible cure, but after contating my local garage and making some enquiries i was informed that my car already had the updated software, and that changing the tcu would cost in the region of £900- £1000 so without being 100% certain this will work i'm reluctant to have it done.
this problem is pretty annoying so it would be good to get to the bottom of it,
is replacing the torque convertor an expensive option?

 

[Bobby Dazzler]

I doubt the lock up clutch is locking at 1500 rpm, more likely the car is changing gear. Mine changes at 1500 on light throttle.

Drive the car and count the changes or after it has changed pull the stick to engage first and see if it changes back down, alternatively try the winter selection to see if it stops the jerk at the set road speed.

Yes I've tried both and it's not changing gear. Revs don't drop at all. Revs climb to the jerk, it jerks, and then continues to climb. Seems like par for the course, but I think I might get it in the dealers to see what they can find out.

 

[Bobby Dazzler]

this problem is pretty annoying so it would be good to get to the bottom of it, is replacing the torque convertor an expensive option?

I think I've always had it too and just assumed it was a gear change, and not given much thought to it. It was only when I started reading about the jerk I thought I'd do some tests in a more controlled way, and sure enough it's exactly as described by other owners.

Trouble is now I know it's there, I keep trying to replicate it, and it's then it becomes irritating. Had I not read the thread I would be blissfully unaware.

I don't think it does any damage, given the large number of owners that have had it a long time, it's just a touch irritating!! Grr.

Replacing the torque converter may have an effect but US owners that have had the whole transmission replaced report it comes back after 1000 or so miles. Suggesting it's adaptation settings in the software.

I cleared the adaptation settings on Friday night when I parked. Will see in the morning if it's still there.

I'll keep you posted when I take mine back to the dealer - still warranted up.

 

[timberman]

I cleared the adaptation settings on Friday night when I parked. Will see in the morning if it's still there.

I'll keep you posted when I take mine back to the dealer - still warranted up.

funnily enough mine always seems to improve for a while after the adaptions have been cleared making me also think its a software fault.

good luck at the dealers, hopefully they'll be able to get to the bottom of this and you can report some good news

 

[v_man]

Hi there.

My 01 W203 had similar symptoms, but was jerking whilst the car was idle (with the foot brake applied). I went away on holiday, came back to a dead battery. Merc assisstance said the memory seats were faulty and were draining the battery. The car was then taken to the dealers who fixed the seats, but needed to reset the TCU as a result. The car came back and the jerk was gone.

Don't waste any money before you've tried the re-flash.

 

[blackscooby]

I'll try mine at low revs. I think mine "jerks" slightly at 1500 RPM. I always thought it was the SuperCharger engaging, certainly as soon as I feel it, and a have the window down I can hear the whine of the S/C.

I'm back in the UK next Saturday, so I'll let you know after that.

I know as soon as I'm back the biggest jerk in the car sits in the drivers seat !

Mind you I had an issue on Saturday. Moved the car to wash it (say 20 feet) engine cold, found I couldn't reach with the hose pipe. Got in to move it again and the darned thing would bearly start... spluttered into life. Almost as if when I shut off the engine it was far too rich, and caused it to flood when I attempted to start again. Never had that before.

**Edit**
I've just been reading the Yank MBWorld and there's a number of threads on this issues, from gentle jerks (so to speak), to rear ended style *BAM* as they put it.
I haven't found any one solution yet in the threads, but as I'm working in Turkey I should have enough time on my hands to have a proper read !!!

 

[Bazzle]

After you do the trans Adapation reset (carsoft etc)
ensure you start engine, put into drive
hold foot on brake for 1 minute.

This learns the torque conv.

Bazzle

 

[sdaushvili1]

Do you guys still have the jerk issue when the engine (maybe the transmission) is properly heated?

 

[Bobby Dazzler]

The characteristic is ever present in most cases. Unless you think it's really bad then there's nothing to worry about.

 

[sdaushvili1]

thanks a lot!

 

[Billy albert]

Ok going to bump this thread as I am looking for the solution and can't find it , does resetting the tcu fix this , how do I do this ?

 

[Billy albert]

After you do the trans Adapation reset (carsoft etc)
ensure you start engine, put into drive
hold foot on brake for 1 minute.

This learns the torque conv.

Bazzle

how ??

 

[MR-AUTOMATIC]

Hi all where do i start 1st thing holding your foot on the brake for 1 minute does not learn the torque converter 2nd thing the price of a rebuilt torque converter with a lifetime warranty is apporx £250.00+vat 3rd thing if you drive the car with the scan tool connected you can immobilise the torque converter from engaging so that would tell you if it was a torque converter fault or not 4th thing a faulty F1 freewheel in the transmission can cause a jerk changing from 1st to 2nd gear if i can help with any more info let me know