W212 E250 Petrol Auto Transmission Downshift Clunk

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Hi all,

I'm having an intermittent issue with my W212 E250, 60k mileage 2013, petrol auto.

When motorway driving - if I put my foot down the transmission would downshift from gear 7 to say gear 5.... now just before gear 5 engages sometimes the transmission would clunk and cause the car to violently jerk forward. After that everything is fine!

I first noticed this 3 weeks ago - I travel 50 miles a day on the motorway.

It has only ever happened during a hard downshift of 2 gears (e.g. gear 7 > 5). Not had any other issues with the transmission and the ATF was changed at 40k miles.

It's an intermittent issue - I can't always replicate it, however I have noticed it is more likely to happen if I put my foot down as I'm travelling up an incline and it downshift over 2 gears (e.g 7 > 5).

Does anybody have any words of wisdom? :)

I have an iCarSoft fault code scanner, will plug it in and see the fault codes this weekend.
 

JBell

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When was the gearbox last serviced?
 

V6Matty

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I have that before and very difficult to replicate, nothing to worry about and essentially your somehow just catching the gearbox out and it thumps into the gear it needs,
 
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When was the gearbox last serviced?
I haven't serviced the gearbox other than changing the ATF and filter at 40k miles. Wasn't aware there is anything else to service?
 
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I have that before and very difficult to replicate, nothing to worry about and essentially your somehow just catching the gearbox out and it thumps into the gear it needs,

Hmmmm... that was my impression too but it's quite a violent thump that jerks the car forward so was a little worried.

In my Layman's thinking process I thought maybe the ATF fluid has dropped and that's why the thump/clunk happens more on a incline (the gradient of the incline makes the low ATF fluid level more apparent)?
 

JBell

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I haven't serviced the gearbox other than changing the ATF and filter at 40k miles. Wasn't aware there is anything else to service?

ATF is 5 years then every 4 after that
 

V6Matty

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Hmmmm... that was my impression too but it's quite a violent thump that jerks the car forward so was a little worried.

In my Layman's thinking process I thought maybe the ATF fluid has dropped and that's why the thump/clunk happens more on a incline (the gradient of the incline makes the low ATF fluid level more apparent)?
Could be just a little low too but only marginally, as I say I’ve had that thump, normally I can recreate it on a specific roundabout in Nottingham onto a duel carriageway, the box is just ready to change up a gear and I floor it catching it out, then it thumps into the lower gear and as you it a BIG thump,
 
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Thanks V6Matty. Yes -it almost feels like I'm catching the gear box out, it gets confused and thumps the gear in place!

I'll keep an eye on this.. if it becomes more frequent then I think that's a sign that something is wrong.

I've not experienced this before with other auto's so was quite surprised the first time it happened!
 
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Hi all,

The above issue is getting worse.

This thump is happening more regularly upon a downshift at speeds of over 40mph and when I press moderately hard on the accelerator.

Yesterday, as it downshifted from 7 > 6 it thumped about 4 times. As I continued my journey I noticed the manual gear change flappy paddle's didn't work anymore and the car displayed that it was in 'D7' regardless of the actual gear it was in.

I parked, switched it off and back on and then the manual gear change flappy paddles' worked and the car was displaying the correct gear in the dashboard.

How odd! I drove it this morning but was careful not to downshift and the car was fine.

I think I need error codes but my iCarSoft 980 is playing up so might have to take it to a garage. Any thoughts?
 

mioba

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Have the tranny and engine mounts checked.

Mercserve in Nottingham,
Radford Road have been looking after my cars for years. I cant recommend them enough. Roger and Nate are top blokes.
 

MBDevotee

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Dreaming of a CL55k - one day maybe....
Gearbox oil / atf leak?

I had this on an old 5sp CLK and it was the rear gearbox oil seal allowing level to drop.
 
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Thanks guys. Had the AA come have a look this morning.

No signs of leak from gearbox, fault scanner revealed:

P033904 - crankshaft position sensor 1, intermittent fault in sensor
P06DA0 - engine oil pump bypass solenoid valve open circuit / electrical fault

The very helpful AA chap explained he thinks it probably is the crankshaft sensor.... Will be off to my garage at some point this week and will update.
 
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Not sounding great. Took it to MB main dealer. They topped up the ATF which was 1L short although no signs of a leak and did a gearbox software upgrade hoping it will fix things but it hasn't.

Further testing will be done today :-(
 

ajlsl600

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Sticking solenoid,control valve in trans ,tc ?
Trans Oil and filter change wont hurt at all. If thats no help see about having the trans re learn yr driving style .and or find a decent indy. Personally I would try a good thrashing followed by oil,filter change first.
 
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ATF and filters were changed at 40k. It's now on 60k.

MB said there were no fault codes stored in the car.

I don't think a good thrashing / re-learn would help. There's something clearly wrong here, it's a harsh/violent jerk followed by a loud thud noise; the issue is quickly provoked under full acceleration but doesn't always occur when when under full acceleration
 

ajlsl600

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No faults shown oil n filter good......invest an hr or so of decent indy time. Go from there.do come back when issue resolved.
 
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The car is at MB main dealer at the moment, lets see what they say today. Hopefully they can diagnose it, then depending on the quote given to rectify I may decide to take it to an Indy.

Will keep you updated
 

John Laidlaw

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This has all the hallmarks of a conductor plate failure except normally it's a one way street , less often intermittent. Very common sadly....
 
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Dare I ask, is it a costly fix? :(
 

John Laidlaw

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Not overly so , I'm not so up to date but the kit is £150/£180 range , plus mechanic time to fit, complete guess 3 hours?
One of the Indy's on here can give you a better idea....
@alexanderfoti is Kent way depending which part of London you are so should be able to help?
 


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