722.9 Auto Gearbox issue *Juddering*

[allybassman]

Hi All,

Strange issue that my 2012 C Class (58k miles) has developed - Upon light load on the engine (keeping pace with traffic between 30-50 MPH I have started to feel the car judder. Accelarating is fine, the gearbox changes smoothly, doesn't hold onto gears too long and behaves normally.

It's when I get up to speed and lightly release my foot off the accelarator to feather it to keep my speed to the desired level is when the issue happens. The gearbox drops into a higher gear to reduce the revs as normal and once it's done that, if I press the throttle, after a few seconds it starts to judder and you can see the rev counter bouncing by a few hundred revs up and down. It's really noticeable if i'm going down hill and I press the throttle pedal lightly.

If I give it more throttle, the issue goes away, if the box changes down a gear the issue goes away too.

I've only owned the car a year - from the service history I can see that the gearbox fluid + filter was changed in March 2015 @ 18k miles. I'm wondering if it's telling me it needs a gearbox service or there is something more drastic wrong!

Thanks for reading

 

[Wighty]

Hi All,

Strange issue that my 2012 C Class (58k miles) has developed - Upon light load on the engine (keeping pace with traffic between 30-50 MPH I have started to feel the car judder. Accelarating is fine, the gearbox changes smoothly, doesn't hold onto gears too long and behaves normally.

It's when I get up to speed and lightly release my foot off the accelarator to feather it to keep my speed to the desired level is when the issue happens. The gearbox drops into a higher gear to reduce the revs as normal and once it's done that, if I press the throttle, after a few seconds it starts to judder and you can see the rev counter bouncing by a few hundred revs up and down. It's really noticeable if i'm going down hill and I press the throttle pedal lightly.

If I give it more throttle, the issue goes away, if the box changes down a gear the issue goes away too.

I've only owned the car a year - from the service history I can see that the gearbox fluid + filter was changed in March 2015 @ 18k miles. I'm wondering if it's telling me it needs a gearbox service or there is something more drastic wrong!

Thanks for reading

I think initially you could do with seeing if any fault codes have been logged . An ICarsoft code reader would do , or MB Star diagnostics at an Independent (probably better for in depth gearbox fault finding) .
A gearbox oil and filter change may well help but that could cost £250 and may not be the fault .

 

[alexanderfoti]

I agree, code check then gearbox oil service (filter and oil change) and see what happens. If the problem is still there, could be TC lockup solenoid or TC itself, they both give issues unfortunately.

 

[allybassman]

Thanks for the replies - I'm hoping it's not the TC but it well could be!

This morning it behaved better - it's more noticeable when the car is cool and only done a few miles - again only under very specific circumstances of low load + high gear so the RPM is around the 1.1-1.3k rpm. After 30 minutes or so it's hard to recreate the issue. My googling is pointing towards TC valve? Either way I'll get it booked in to a local Mercedes Specialist.

 

[Wighty]

Thanks for the replies - I'm hoping it's not the TC but it well could be!

This morning it behaved better - it's more noticeable when the car is cool and only done a few miles - again only under very specific circumstances of low load + high gear so the RPM is around the 1.1-1.3k rpm. After 30 minutes or so it's hard to recreate the issue. My googling is pointing towards TC valve? Either way I'll get it booked in to a local Mercedes Specialist.

May well be fluid level ? When the oil warms up the volume expands and then becomes the correct fluid level .
Let us know how you get on

 

[alexanderfoti]

The TC can be turned off temporarily on the mb diagnostics tools, to rule out whether shifting characteristics are from the gearbox or TC.

 

[allybassman]

Thanks chaps, i've booked it in with the receptionist as a gearbox issue rather than just a service. When I drop off i'll explain the issue and let them diagnose and advise rather than trying to be a know it all and telling them what to do haha!

 

[ajlsl600]

TC related . this car has trans cooler ? water getting in oil ? advise getting codes read first.

 

[allybassman]

Just to add further symptoms / observations. Start of my journey it was easy to feel / produce the issue. Drove a few miles to Shell to fill up with my usual V-Power Derv. As soon as I left the forecourt a DPF regen started, the gearbox started behaving, due to gears being held and revs not going below 1.5k even when cruising. I took the long way home to let the DPF regen finish and as soon as it did and things were nice and hot the shifting quality felt better and even if I tried, I could not get it to judder.

 

[Gazwould]

Hmmm , V Power derv , could you tell me the Cetane number improvement over standard ?

 

[allybassman]

Hmmm , V Power derv , could you tell me the Cetane number improvement over standard ?

Christ no - not starting this old debate! Always used it (and the petrol) probably always will.

 

[Gazwould]

Lol , fair enough , big con though as Cetane number isn't disclosed unlike petrol pump Octane .

 

[allybassman]

I use it more for the additives to be honest - I used to have a MK1 Skoda Fabia VRS many moons ago that ran better on Standard Diesel + manually adding Cetane booster / cleaning additives products - After a while it became a bit of a faff, so I started using V-Power (sceptical at first) and found it ran just as well - so every Diesel and Petrol car since has used Shell V-Power. it's a shame they have changed the drivers club points system - but that is a whole new debate!

 

[Gazwould]

Started using 2 Stroke in the PD and it halved the smoke opacity test .

Now use it along with 40ml of 2-EHN with the mixture easily added in used Redex bottles .

 

[allybassman]

just returning to update this thread,

After weeks of every journey having this issue numerous times and being able to easily re-create it, the juderring suddenly went away / happened every so often.. typical as I had my car booked in with a reputable Mercedes specialist. I kept the appointment and took it down, they did a road test / scanned using STAR and found no faults (again, typical!) They advised that as the gearbox was due a service soon it would be a good idea to get it done now incase it's related to old fluid.

I got the car back and noticed straight away that the quality in shifts is much better, especailly 2-3 3-4 even when cold! I've not done a massive amount of miles since, so fingers crossed it's gone.

 

[allybassman]

An update I was hoping not to give!

The issue has come back, a few hundred miles after the fluid change I was starting to get the judder again under the same conditions. My reading up on Auto boxes has led me to believe that it's when the TC locks-up that I get the issue.

Some journey's I get it intermittently, sometimes not. Even more frustrating is that no codes are logged and when scanned with Star - nothing is brought up.

To get around the issue, if driving around town, I use the paddles to put the car into D4, this seems to stop it happening.

 

[bembo449]

Some wont agree with this but you could of added some tranny shudder fix with the fresh oil change on the box , ive used it and i know others that have too with great results

 

[pgh13]

An update I was hoping not to give!

The issue has come back, a few hundred miles after the fluid change I was starting to get the judder again under the same conditions. My reading up on Auto boxes has led me to believe that it's when the TC locks-up that I get the issue.

Some journey's I get it intermittently, sometimes not. Even more frustrating is that no codes are logged and when scanned with Star - nothing is brought up.

To get around the issue, if driving around town, I use the paddles to put the car into D4, this seems to stop it happening.

Do you know how much fluid was changed? If its drained and the sump dropped that's only about 3l. There's more than twice that in torque converter and cooler. What some do is disconnect the cooler return and run the engine to pump 3l through, then stop and top up and repeat the process, and possibly once more. Admittedly, its more of a pita with the fill from the bottom 722.9, though.

 

[matthew k]

If it's happening in higher gears under TC lock up conditions it's releated to the increaed amount of tourqe being placed through it. This would suggest a problem with the torque converter or the friction plates themselves.

Did they check the fluid for contamination when they changed it?

 

[allybassman]

If it's happening in higher gears under TC lock up conditions it's releated to the increaed amount of tourqe being placed through it. This would suggest a problem with the torque converter or the friction plates themselves.

Did they check the fluid for contamination when they changed it?

That would make sense, my research was pointing towards that issue... not good!

Nope, they did not mention the condition of the fluid removed, I also don't know the amount they changed.. I really did think the issue was cured, for weeks it was fine and then all of a sudden it started creeping back. It's certainly not as often as before, but this may be due to me driving around the issue.