Knocking on steering on new GLC

[JohnM]

Perhaps the RHD vehicles have a different type of clutch? There are differences between models, see the Breakaway Clutches part of this description (though it is from a few years ago): Mercedes-Benz Four-Wheel-Drive In-Depth Look | eMercedesBenz

 

[HumberMart]

Perhaps the RHD vehicles have a different type of clutch? There are differences between models, see the Breakaway Clutches part of this description (though it is from a few years ago): Mercedes-Benz Four-Wheel-Drive In-Depth Look | eMercedesBenz

I see that all LHD GLC's have a multi plate clutch in the transfer box.

Could it be that RHD's have only a single plate due to space issues? In other words the only way they could make a RHD 'GLK'.

When I drove a C43, I was bothered by the extra wide tunnel pushing my left leg too far right.

 

[John Jones Jr]

I see that all LHD GLC's have a multi plate clutch in the transfer box.

Could it be that RHD's have only a single plate due to space issues? In other words the only way they could make a RHD 'GLK'.

When I drove a C43, I was bothered by the extra wide tunnel pushing my left leg too far right.

I was thinking along those lines but I've no idea regarding the differences between L/H and R/H/D setup or installation of the front diff.

http://www.mbclub.co.uk/forums/whee...g-near-full-steering-lock-14.html#post2408313

 

[talltrees]

I had the car for many months/miles since last February and thought this problem did not apply to me.
It was only when we had snow last week and grip was much less that I really noticed it. I now think it has been doing it all along and I just thought I was going over a bump which was unsettling the car.

What I don't understand; if this is a loss of grip in the tyres then It should be noticeable in the tracks in fresh snow last week but there was absolutely no sign of any deviation/ slip or judder at all. So I think its in the drive line myself.

 

[grober]

All I can re-iterate is that according to WIS two different transfer boxes exist. One with single stage planetary gears 39/61 [RHD] and one with two stage planetary gears 45/55 torque split. [LHD] Whether they also differ in having a multi or single clutch design I can't comment. Unfortunately there is no exploded parts diagram in the EPC since it would appear these boxes designed to be replaced as complete units.
http://www.mbclub.co.uk/forums/2400635-post117.html

ps
a picture of theold 4matic system but might illustrate a two stage planetary gear set ?

later setup pictures which appear to be two stage also but difficult to make out any multiplate clutch?maybe in front of the planetary gearset?

or

 

[grober]

This is a good explanation of how the old 4matic system worked
gapr99p24
Its perhaps interesting to note there are two lock up clutches in the old system which are either on or off 1 on the centre planetary gear differential and 2 on the front drive engagement --- meaning that in certain circumstances the old system can revert to RWD alone. Pretty sure this doesn't apply to the latest setup. Anyway maybe explains a bit more?

ps it has been suggested elsewhere that the "multiplate clutch" in the MRA rear drive architecture 4wd transfer box does not have the same sophisticated function as the "on demand " electronically controlled multiplate clutch pack in the the MFA front wheel drive version of the 4matic. There the multiclutch alters drive to the rear wheels on demand i. e. as much as the 4matic determines.

Instead it functions a bit like an electric drill simple spring loaded "safety clutch" to actually prevent transmission wind up and subsequent damage in extreme circumstances. As such its function is going to be pretty crude [ on off] and maybe its this that folks are experiencing? If indeed its that then it is functioning as designed.
Just a theory??

 

[190]

It looks to be a complex system and must be expensive which I suppose is why MB are reluctant to modify it.

You have to wonder how many owners really need 4WD of this sophistication. 2WD and a set of winter tyres would be a lot simpler and cheaper.

 

[Dryce]

2WD and a set of winter tyres would be a lot simpler and cheaper.

I don't think all customers for these vehicles are so bothered about snow.

These things are bought for various reasons - including image.

But also as a security blanket for people who occasionally take their vehicles into unpaved areas.

 

[grober]

Folks might be interested in this thread.
New Transfer Case at 10,000 miles? - Mercedes-Benz Forum
which gives details of Mercedes-Benz TSB LI28.00-P-051499

 

[dejongj]

Wow - this is getting worse for Mercedes. Interesting review of the E43 and ahem also affected by build in crabs

Mercedes-AMG E43 Estate: Driven | PistonHeads

 

[trapperjohn]

Could it be that various Forums, Piston Heads and testers are finally exposing a very significant issue for Mercedes here.

Our own little forum (I don't usually read others) seems to have a good grip on what could be happening.

 

[Bluegnomes]

From todays Pistonheads review of the new E43 estate

As in the C-Class though there seems to be some clunkiness in the application of the system. In the C43 we noticed some chuntering on full lock and at low speeds, such as pulling out of parking spaces. In the E43 it's arguably even more noticeable, the front wheels 'skipping' as if there's some transmission wind or a locked diff somewhere in the system. Interestingly the Porsche Panamera 4 S we've got in at the moment does the same thing, albeit to a lesser extent and Mercedes is promising to get back to us since raising the issue

This seems like a characteristic across the 4matic range?

 

[dannycotw]

This seems like a characteristic across the 4matic range?

My Audi S3 didn't do it, my BMW 3 series x-drive didn't do it, Volvo XC60 didn't do it so why can't MB engineer their cars not to do it?

 

[DRIVER200]

My Audi S3 didn't do it, my BMW 3 series x-drive didn't do it, Volvo XC60 didn't do it so why can't MB engineer their cars not to do it?

Unfortunately its not just MB the mighty Porsche has cars in its range that do it but they choose not to engineer it out. See recent Pistonheads report below on the new MB E43 which also mentions the new Porsche Panamera 4S. My personal theory is that Porsche are supremely confident that people will buy their cars no matter what so a relatively small problem like this doesn't bother them.

''As in the C-Class though there seems to be some clunkiness in the application of the system. In the C43 we noticed some chuntering on full lock and at low speeds, such as pulling out of parking spaces. In the E43 it's arguably even more noticeable, the front wheels 'skipping' as if there's some transmission wind or a locked diff somewhere in the system. Interestingly the Porsche Panamera 4 S we've got in at the moment does the same thing, albeit to a lesser extent and Mercedes is promising to get back to us since raising the issue.''

 

[tonysmb]

I was just about to post a link to the issue raised on PH but, as usual, I'm behind the times.

 

[DRIVER200]

I was just about to post a link to the issue raised on PH but, as usual, I'm behind the times.

Just to rock my theory a little when it comes to Porsche and MB making RHD cars with 'Characteristics' that may not please all drivers its worth remembering that their main market is North America and Europe which obviously have LHD so this particular problem is non-existent in these places otherwise it would no doubt have been sorted by now.

 

[henryc1]

Another sufferer

I have been following this thread with increasing disappointment in Mercedes and their reaction.

I picked up my GLC Sport 220D with off road pack (not air suspension with 18 inch wheels and the Hankook tyres) in September 16 and noticed the knocking, noise or scrubbing on full lock going into my drive within a week. I did notify the dealership by email but as the scrubbing or wheel slip only happened in the drive (but not every time) I told them I would wait until I could reproduce the effect to demonstrate it to them.

I copied this from Mercedes Uk website under Driving Dynamics


"The GLC handles with all the precision and composure you expect from a Mercedes-Benz. Even in challenging driving conditions, 4MATIC permanent all-wheel drive is on hand to optimise traction and ensure superb response. The system has even been specially tuned for right-hand drive vehicles, with a 39:61 torque distribution between front and rear axles to enhance driving enjoyment and control."

I will continue to follow this topic and will report any developments.

 

[dejongj]

I've now seen further reports from down under where they are suffering this as well. Interesting as at the moment temperatures rarely go under 20 degrees. The chap was saying it mainly happens when the road is wet.

Winter tyres my ****.

 

[Toobad]

So the MB UK website is claiming all RHD GLC models have a 39:61 torque distribution. I wonder if this could be cross-checked against another source? After all, in the current climate, it is very hard to take anything MB UK says as gospel. In the Autoexpress review it says:

"Theoretically, the higher-powered car should be more fun to drive, thanks to its 31:69 front-rear torque split, but in all honesty you’ll struggle to tell the difference between this and the 45:55 separation on the GLC 220d."

I assume they were given these specs in an MB Press Pack to use when writing their review.

Auto Express review of Mercedes GLC

 

[tonysmb]

Taken from All Wheel Drive Explained | awd cars, 4x4 vehicles, 4wd trucks, 4motion, quattro, xDrive, SH-AWD, Haldex, Torsen, wiki - How it works

Assuming that the "differential lock" function on the same axle is taken care of by Mercedes usual selective braking via the antilock/stability control system then cross axle transmission wind up should not be a problem. On the front axle there might be steering scrub if true ackerman steering is not present [ i.e. each front steering wheel to be at a slightly different angle in order to trace out a slightly different curve radius]---- I guess when the wheel is driven this might present as a series jumps or clonks????

However- the front and rear wheels also have trace out a different curve radius. Again wheels on the same rear axle present no problem with an open diff.
Which leaves us with the prime candidate for transmission wind up [ front to rear- not side to side!] IF!!! the centre differential is locked or close enough to locked meaning the front and rear wheels can't rotate at sufficiently different speeds while necessarily tracing out their different radius curves.
My theory is that some sort of effect like this may be exacerbated by the 39/61 torque split if indeed LHD cars don't suffer from this with their 45/55 split ?

While for driving on grippy pavement at slow manoeuvering speed at full lock it might be useful to program the centre diff to disengage at high steering angles its possible to envisage this as a situation where full 4WD might be very advantagous when trying to manoeuvre/ start off on very slippery /snowy conditions. Its perhaps the sort of ability lots of owners would expect ---nay demand from their 4WD vehicle. In the old days all these differential locking actions were manually selected by the driver as appropriate to conditions but now its all automatic meaning perhaps there has to be compromise somewhere.


or something like that.

I have no doubt it's related to this, which was my first thought when I first saw the thread. Anyone who has driven the old type of manual locking centre differentials (ie the original early Range Rovers) with them locked on a hard surface will have experienced the juddering /clunking as the wheels try to 'spin' momentarily to release the 'tension' in the system; unless it breaks first.

Modern systems are more complex and some are electronically controlled, but the same laws of 'physics' apply.

It might be typical of the parameters built into the system, much like a GT-R transmission 'grumbles' and shunts in low speed manoeuvring. Whether a GLC should be like that is a different question.

I don't see that 7 degrees C is a magical figure.

Has anybody with an affected car tried driving it on, for example, wet slippery grass and, if so, does the car still exhibit the same tendencies?