Gearbox Problem?

[Poolie]

Hi All

I'm new to the site and only recently bought my 2006 CLS CDI 3 litre (around 98k on the clock) and thoroughly loving owning the car, it's great to drive, like driving an armchair...but looking for a bit of help please. Oh, I'm no mechanic either.

I'm experiencing a few intermittent faults all, seemingly, linked to the gearbox but like I said, I'm no mechanic....here's what I'm experiencing occasionally..

1) Pull up to lights/sat in traffic for not very long and I don't like sitting with my foot on the brake (for the person behind me staring at brake lights) so I tend to put it in neutral or park. When I leave it in neutral before going back in to drive sometimes the automatic gearbox doesn't change gear, it moves but I could be sat at 30mph doing nearly 3k revs. Going from park to drive doesn't tend to cause any issue. It always rectifies when I turn off the engine then turn it back on - not really ideal. Is there anything you could suggest or any glaring errors I could be making?

2) Very occasionally there's quite an audible 'clunk' from behind me when going from park to drive. Any ideas? Doesn't do it all the time, far from it.

Any help is much appreciated and please let me know if you need more detail.

Thanks

 

[Blobcat]

Hello and welcome,

Leave it in drive and use the foot operated handbrake (or brake hold - additional press on the brake pedal once stopped)

You have the 7G box which can be clunky initially - get the ATF changed in not done so (should be every ~37K miles).

 

[onefortheroad]

Brake lights still light up using hold . Ideally you need to stop thinking of those behind and just sit with your foot on the brake.

 

[Srdl]

Welcome. First check is that the ATF has been changed on schedule.

 

[Blobcat]

Brake lights still light up using hold . Ideally you need to stop thinking of those behind and just sit with your foot on the brake.

They do, less leg strain using hold though

 

[Wighty]

Hi All

I'm new to the site and only recently bought my 2006 CLS CDI 3 litre (around 98k on the clock) and thoroughly loving owning the car, it's great to drive, like driving an armchair...but looking for a bit of help please. Oh, I'm no mechanic either.

I'm experiencing a few intermittent faults all, seemingly, linked to the gearbox but like I said, I'm no mechanic....here's what I'm experiencing occasionally..

1) Pull up to lights/sat in traffic for not very long and I don't like sitting with my foot on the brake (for the person behind me staring at brake lights) so I tend to put it in neutral or park. When I leave it in neutral before going back in to drive sometimes the automatic gearbox doesn't change gear, it moves but I could be sat at 30mph doing nearly 3k revs. Going from park to drive doesn't tend to cause any issue. It always rectifies when I turn off the engine then turn it back on - not really ideal. Is there anything you could suggest or any glaring errors I could be making?

2) Very occasionally there's quite an audible 'clunk' from behind me when going from park to drive. Any ideas? Doesn't do it all the time, far from it.

Any help is much appreciated and please let me know if you need more detail.

Thanks

As above , when was the last gearbox service ?
If the fault rectifies when the car turns on and off again , then have the car scanned for fault codes .
Where do you live so someone can recommend a specialist.
Is that the V6 engine or the IL6 one ?

 

[rich.g.williams]

I could have suggested a few things if it was the 5G-Tronic box but I don't know much about the 7G-Tronic. From what you say the transmission controller (ETC - inside the gearbox) is loosing track of what's going on for whatever reason. By turning the engine off, the hydraulics (because pressure is lost) and the electronics (because power is lost) return to default states and all is well again.

The clunk you sometimes feel hopefully just results from the ETC having lost control. There could be other more mechanical reasons for the clunk.

As mentioned holding the brake staying in Drive is a workaround but an unpleasant workaround with safety considerations - better that the transmission works as intended.

Best get it looked at.

 

[onefortheroad]

They do, less leg strain using hold though

Knee strain even if you've a prosthetic limb.

 

[rich.g.williams]

Very occasionally there's quite an audible 'clunk' from behind me when going from park to drive

That could be unrelated and coming from the drivetrain further back than the transmission (prop shaft couplings, differential, even wheelnuts). Maybe check to see if it happens when going from driving forward to reversing at slow speed.

 

[Poolie]

Thanks for all the responses, much appreciated....all I can tell you is that it has a full service history at either a main dealer of a Merc specialist (the stamp for the specialist is Godstone Mercedes at RH9 8NE) and the last service was August last year (just over 90k miles) and the book says it was a 'C' service. I've looked through the rest of the service books and can't see that the ATF replaced has been ticked anywhere!

My nearest Merc specialists are Merxworx and Mer-Tech (both Hull) so if anyone knows anything about either I'd be grateful.

 

[Botus]

full service history = the engine oil was change once a long time ago (usually with a budget brand of the wrong grade)

most trans issues - in the old days were due to insufficient / overheating fluid, this leads to wear and even more overheated fluid in a viscous circle - not much has changed... aside from they added electronics to make things even worse

it's good to get the gunk out - even if its just so you can see when needing to pull it apart for further work -thus new fluid and a filter that actually lets it circulate is often the cheapest starting point

 

[Poolie]

Ok so the problem has developed a bit…it now won’t change gear at all and the sport button doesn’t work.

Every time I go from park or neutral to drive I hear and feel a clunk from behind me and the gear doesn’t change when accelerating even after restarting the car.

Please tell me this isn’t a new gearbox

 

[malcolm E53 AMG]

These gearboxes use speed sensors so that the gearbox ECU knows when to change gear so it’s very likely the electric plate which houses the speed sensors is failing/failed so you need to take the car to a MB specialist have the codes read to be sure and have the gearbox serviced and possibly the electric plate replaced. I’m not sure but early 7 speed boxes 05/06 had the electric plate/valve block combined so hopefully not yours

 

[Poolie]

Forgive my ignorance but if the electric plate/block are combined is this a new gearbox?

 

[malcolm E53 AMG]

Forgive my ignorance but if the electric plate/block are combined is this a new gearbox?

No, but it is a larger component, not sure of the cost but could be £800+

 

[onefortheroad]

Forgive my ignorance but if the electric plate/block are combined is this a new gearbox?

I found an ECU repairer, most are £250 .

7G-Tronic transmission - TCM conductor plate failure

Mercedes 7 speed transmission ECU (722.9 gearbox) is a common failure to cause gear selection problems, test and rebuild of your 7G-Tronic ECU

www.ecutesting.com

A gearbox specialist will still charge labour to get it out and then replace .

 

[Poolie]

That’s very helpful thank you. £250 sounds much better than £800+!!

I was trying to hold off getting it looked at because the MOT is due shortly so to save an extra trip to the garage I was going to do it at the same time. No choice now!

Is it safe to drive in the meantime? Albeit at 30mph at 3k revs or will I do more damage?

 

[LostKiwi]

Get the codes read before spending money. An iCarsoft costs under £100 (or an Autel AP200 is even cheaper).

 

[Poolie]

Again, please forgive my ignorance but what is an iCarsoft and an Aurelius AP200?

I spoke with a merc specialist the other day and they quoted £65 to check the gearbox (as in check for faults before doing any work), is this reasonable?

 

[Blobcat]

Again, please forgive my ignorance but what is an iCarsoft and an Aurelius AP200?

I spoke with a merc specialist the other day and they quoted £65 to check the gearbox (as in check for faults before doing any work), is this reasonable?

They’re OBD scanners that can read error codes