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This is one of the best descriptions of this problem in Sport+. To expand on it the issue would be as follows for the most common scenario I encounter:
You're approaching a corner that requires braking.
You apply brakes, car changes down gears.
You're coasting around the corner (not accelerating or braking) at around 10mph.
You start accelerating normally, low throttle.
If within 1-2 seconds of this initial acceleration you even lift off the accelerator 1mm the car jerks back massively, as if you've just hit the brake.
I don't think the gearbox has changed gears at stage 4/5. The gearbox is quite rough anyway, in any mode you can get occasional sharp gear changes out of nowhere. I'll try and get the software updated and see.
This^^ has been my experience as well and is why I rarely use S+. In S I can lift my foot off the throttle abruptly with no lurch. If I do it in S+ under circumstances similar to what's described above it will buck and then continue to buck if light, even throttle is applied. The only way to stop it is to come completely off of the gas again or to mash the pedal.
I do think the gearbox has shifted at this point. I have only encountered this situation in 1st gear. I have the HUD in mine so I'm always aware of what gear I'm in.
This^^ has been my experience as well and is why I rarely use S+. In S I can lift my foot off the throttle abruptly with no lurch. If I do it in S+ under circumstances similar to what's described above it will buck and then continue to buck if light, even throttle is applied. The only way to stop it is to come completely off of the gas again or to mash the pedal.
I do think the gearbox has shifted at this point. I have only encountered this situation in 1st gear. I have the HUD in mine so I'm always aware of what gear I'm in.
I've never really used S mode but that's interesting to know. You're right about the repeated bucking as well, forgot to mention that, think I managed to get it to buck 3 times within a couple of seconds the first few times I encountered it before I got my head around it.
I forgot to mention I've done nearly 7k miles so I'm well past the breaking in period (and I've not driven it like a boy racer). I'm going to book it in this week and hope the dealer doesn't try and BS me.
Last edited by ajgraham; 02-03-2018 at 07:16 PM.
Reason: more detail
I've never really used S mode but that's interesting to know. You're right about the repeated bucking as well, forgot to mention that, think I managed to get it to buck 3 times within a couple of seconds the first few times I encountered it before I got my head around it.
I forgot to mention I've done nearly 7k miles so I'm well past the breaking in period (and I've not driven it like a boy racer). I'm going to book it in this week and hope the dealer doesn't try and BS me.
I think the reason the car does not display the bucking in S is because S will hold 2nd gear on deceleration until you are at a complete stop. S+ downshifts to 1st gear around 10mph or so.
I went to the dealer yesterday and they got me to fill out the attached PDF in order to reproduce the issue. I offered twice to show them the issue on a day and time to suit them but the service manager wanted to follow his process. I'll bet $65k they can't reproduce the issue and I end up having to show them the issue myself anyway.
I also asked twice whether or not there is a software update for the transmission and he said they try to diagnose the issue before applying software updates which makes absolutely no sense to me if their is an update available. If this process doesn't work out we'll play hardball.
I tried using the S+ on my 2018 GLC43 during a recent commute and did not experience any jerky response. Having to fill out a form to document an issue seems unreasonable. Why is the service advisor not documenting the issue and the diagnosing it?
Got my car back this morning after them having had it for 4 days. Basically they reproduced the harsh shifts and the scenario that was detailed previously.
They found a low voltage fault code on the gearbox, but they said that was not the cause of the issue.
They checked assembly of transmission, no issues.
Leak test and oil check on transmission, no issues.
Bulletin LI27.00-P060741 relating to shifting complaints appears to involve updating control software on the transmission and they "performed torque converter lockup clutch adaptation and shifting adaptations".
I've tested it this afternoon in various scenarios and the difference is massive. Gear changes are infinitely smoother now, the torque is smoothed out now before and after gear changes even under full throttle. I really should have flagged this issue a long time ago. Hopefully not too much wear has occurred on the gearbox due to the previous harsh gear changes, I doubt it as it was rarely in Sport+ but something I'll monitor.
If anyone is interested I can attach the Mercedes service documents for the work they did, it has a little more detail.
Last edited by ajgraham; 02-09-2018 at 06:14 PM.
Reason: typo
Got my car back this morning after them having had it for 4 days. Basically they reproduced the harsh shifts and the scenario that was detailed previously.
They found a low voltage fault code on the gearbox, but they said that was not the cause of the issue.
They checked assembly of transmission, no issues.
Leak test and oil check on transmission, no issues.
Bulletin LI27.00-P060741 relating to shifting complaints appears to involve updating control software on the transmission and they "performed torque converter lockup clutch adaptation and shifting adaptations".
I've tested it this afternoon in various scenarios and the difference is massive. Gear changes are infinitely smoother now, the torque is smoothed out now before and after gear changes even under full throttle. I really should have flagged this issue a long time ago. Hopefully not too much wear has occurred on the gearbox due to the previous harsh gear changes, I doubt it as it was rarely in Sport+ but something I'll monitor.
If anyone is interested I can attach the Mercedes service documents for the work they did, it has a little more detail.
Awesome, glad you got it taken car of. I'm just about to hit 1000 miles on mine and will be jumping into S and S+ modes soon, so hope this doesn't happen to me. It would be great if you could post the service docs or just type the service they did with any codes/ID's in case someone else runs into this issue.
i actually think the tranny was a bit smoother before - with a caveat
if you let go of accelerator suddenly - it was a mess and jerky
if you remember to do things slowly the tranny was very smooth. agreed not a workable solution for a high end vehicle
i find that the upshifts are about the same, maybe a shade smoother before
but now on the way down i find that the tranny will downshift and revs climb a little bit. before it felt like when slowing down the thing was in neutral and i didnt notice the trannnyslowing the vehicle.
it is noticeable but not awful - and only when i pay attention to it. not noticeable probably to anyone but me and yes it is perhaps in my head because i know they changed something
overall i will say it is a good fix because that crazy jerkiness would even happen in E or C for me and i would have to be vigilant to make sure it didn't happen.
i actually think the tranny was a bit smoother before - with a caveat
if you let go of accelerator suddenly - it was a mess and jerky
if you remember to do things slowly the tranny was very smooth. agreed not a workable solution for a high end vehicle
i find that the upshifts are about the same, maybe a shade smoother before
but now on the way down i find that the tranny will downshift and revs climb a little bit. before it felt like when slowing down the thing was in neutral and i didnt notice the trannnyslowing the vehicle.
it is noticeable but not awful - and only when i pay attention to it. not noticeable probably to anyone but me and yes it is perhaps in my head because i know they changed something
overall i will say it is a good fix because that crazy jerkiness would even happen in E or C for me and i would have to be vigilant to make sure it didn't happen.
From everything I've read about the gearbox it seems due to the learning aspect of the gearbox software that each persons vehicle will drive differently, even outwith any small mechanical differences. If anyone's in or near the Houston area and has a GLC43 I'd be interested to do a comparison. I do wish I'd done some performance benchmarking before having the work done as due to the torque being so much smoother now I can't tell if it's actually slower or just feels slower because I'm not being thrown around by rough gear changes. It's definitely safer than before as it's predictable and the throttle is more linear. I don't want the fix to the gearbox being they've also taken a chunk of HP away, I don't think that's the case but I'll try and test by doing a couple of 0-60's.
I drove my wife to the airport on Sunday and got to test out Sport+ on the highway. Interestingly it will now utilise the 9th gear around 80mph which previously it never did.
ML6.3 AMG – Hill Start problem – 58k miles. Looking at the symptoms listed in this thread, member cahiil55k had the nearest symptoms to mine posted 01-25-2017, however have not found information leading to a cure.
The car will stop suddenly with the brakes being automatically applied after a hill start, when starting off gently at 1000 to 1200rpm. In either forwards or reverse. Starting off with gusto avoids the problem, but of little help when parked between cars on a hill.
Went into MB who were able to reproduce the effects on their multi car park ramps – information sent to MB technical for help – no relevant error codes. Subsequently MB Technical requested changing 4 wheel sensors, which one imagines would have raised error codes if any one of them was faulty, it looks as though a diagnosis has yet to be made.
Further testing since by me showed:-
1. If the hill start is not engaged, i.e. stopping by slowing down then holding it on the throttle (not using the brake pedal) and then starting off, there is no problem.
2. If the hill start is engaged and then the car is held on the throttle without creeping forward or even allowing it to slip backwards slightly to detect when the mechanism has disengaged, there is no problem when starting off. If during this test there is any forward motion before the mechanism disengages - the brakes jam on again.
This ties in with what the MB tech. found when he disconnected the hill start system. i.e. the problem did not occur.
3. Switching off the engine even for a few seconds resets the fault condition so that it is again easily demonstrated. i.e. I drove the car for 20 minutes and parked on a hill probably steeper than the multi-storey car park ramp at MB. A hill start test caused a mild brake application fault condition. Switching off the engine and on again whilst holding the car on the brakes caused the following test to show the fault as severe as when the car is cold.
This changes the characteristics of when the fault is observed: -
The previous supposition that the heat of the engine was important is probably false, instead it is probably how long the engine has been running which decides on how readily the fault can be demonstrated. The heat of the transmission fluid will be a factor on how steep the hill needs to be to show the fault at low revs, because when the fluid is hot it more easily drives the car forward (or backward) and the steeper hill is required to a gentle start in the required rev range of 1000 to 1200rpm.
It now looks as though the problem gradually diminishes the longer the engine has been running, but resets on a restart. Coupled with a required rev range 1000 to 1200rpm this makes me suspect failing capacitors as a potential cause. (my career was in electronics), but I am not familiar with the ML6.3 electrical set up.
Has anyone had a fault like this and what was done to solve it?
ML6.3 AMG – Hill Start problem – 58k miles. Looking at the symptoms listed in this thread, member cahiil55k had the nearest symptoms to mine posted 01-25-2017, however have not found information leading to a cure.
Sorry to read the issues you're having. From my understanding the braking issue that cahill55k wrote about was a misunderstanding to do with the Brake Hold feature in the GLC's (not to be confused with Hill Hold). Not sure which other Mercs have this feature but in GLC's if you depress the brake sufficiently it will hold until you press the accelerator, I think there was some confusion and misunderstanding due to this.
Have you tried in the ML forum? They have a lot of knowledgeable people there and someone else must have had the issue you're seeing.
Just brought a 2018 glc43 in dec 2017. The car got the new 9g enhanced transmission. After driving the car for couple months I have noticed the car got rough downshifting from gear 4 to gear 3 (I only drive the car in comfort mode). Is this normal?
Just brought a 2018 glc43 in dec 2017. The car got the new 9g enhanced transmission. After driving the car for couple months I have noticed the car got rough downshifting from gear 4 to gear 3 (I only drive the car in comfort mode). Is this normal?
My main issue was in Sport+ mode that the throttle had a hair trigger and gear shifts were very rough. I did though have occasional rough gear changes even in Comfort at lower speeds, particularly downshifts.
I'm guessing with your car being new it's still under 1000 miles? If I were you I'd get the car warmed up, put the Dashboard in AMG mode so you can see the engine and gearbox temperatures and once the numbers are no longer blue put it in Sport+ (gearbox will take longer to warm up than the engine). You don't need to floor the throttle to test it out or redline it, even just half throttle and test it going up and down the gears you'll get a feel for how smooth the gearbox is. Test it out and let us know what you encounter.
Thanks again for this info, ajgraham. I had my first experience with this today and holy ***** was it crazy. In Sport+, slowing down to take a right turn (maybe 20-ish mph, 2nd or 3rd gear?), stepped back on the gas and the GLC43 bucked like a wild bronco. I may have minor whiplash... . Not sure exactly what I did to make it stop, but I think I took my foot off the gas completely, slowed down, and then slowly pushed back on the gas pedal. Couldn't do anything too crazy as there was a car fairly close behind. Tried to replicate on the next turn and didn't happen, but I think I almost came to more of a complete stop versus the "bucking" turn where I had a little speed. Off to try and replicate again and then an appointment with the dealer. Crazy...
The scenario you mentioned was exactly the same as mine, it would throw you back and forth if you lifted off the throttle at certain points. Print off the image attachments that I uploaded if the dealer doesn't know anything about it.
Moisture in the distributor cap can cause a car to jerk when accelerating. When a car has been parked overnight in cold temperatures, moisture can form inside the distributor cap, causing the engine to misfire when accelerating. A misfire occurs because the engine power is off balance or uneven. Parking a vehicle in a garage or a warmer environment helps prevent moisture from forming.
If the vehicle continues to jerk while accelerating gradually over a prolonged time period, a vacuum leak may be the cause. A vacuum leak occurs when the fuel system creates a vacuum in the engine, causing the vehicle to spring forward when the gas pedal is pushed. The vacuum leak sends an incorrect amount of fuel to the engine, causing the vehicle to jerk when accelerating.
If the vacuum leak is not the cause, a car may also jerk when accelerating if it has a faulty throttle position sensor. This occurs in vehicles equipped with a fuel-injection system. Once the gas pedal is pushed, the data in the sensor allocates a certain amount of fuel to disperse. When the throttle position sensor is faulty, it transmits incorrect data, which in turn sends the wrong amount of fuel to the engine.
Got my car back this morning after them having had it for 4 days. Basically they reproduced the harsh shifts and the scenario that was detailed previously.
They found a low voltage fault code on the gearbox, but they said that was not the cause of the issue.
They checked assembly of transmission, no issues.
Leak test and oil check on transmission, no issues.
Bulletin LI27.00-P060741 relating to shifting complaints appears to involve updating control software on the transmission and they "performed torque converter lockup clutch adaptation and shifting adaptations".
I've tested it this afternoon in various scenarios and the difference is massive. Gear changes are infinitely smoother now, the torque is smoothed out now before and after gear changes even under full throttle. I really should have flagged this issue a long time ago. Hopefully not too much wear has occurred on the gearbox due to the previous harsh gear changes, I doubt it as it was rarely in Sport+ but something I'll monitor.
If anyone is interested I can attach the Mercedes service documents for the work they did, it has a little more detail.
My service representative said I have the same issue (low voltage fault). However according to him, he has to replace the gearbox chip and order updated one from Germany to make sure this won’t happen again.
My service representative said I have the same issue (low voltage fault). However according to him, he has to replace the gearbox chip and order updated one from Germany to make sure this won’t happen again.
Thanks for the info. Did you have the same gearbox issue as well? Which country are you based in? Did the paperwork mention any bulletin numbers for the chip replacement?
The interesting thing is that about 6 weeks after I had the corrective work done, I put it in for it's Service A which seemed to reset the gearbox and it was rough again. A week later I had to get a tyre replaced due to yet another puncture and for some strange reason afterwards the gearbox was again smooth. I can't explain why it changed back and forth when neither the Service A or tyre replacement should have affected the supposed fix for the gearbox. If the issue reoccurs with mine I'll push for this fix.
I've induced the violent gear lash buck once so far in sport+ at about 20-30mph with GO/nogo/go gas pedal. I have about 1.5k miles on. Sport+ requires a huge 'commitment' and traffic generally won't allow it. To me, sport+ is almost not streetable. The super short throttle travel, super quick tip in, and numerically high ratios cause a resonance that swings between accelerate/decelerate where engine and body are opposite. Bucks so hard the gas foot can't help but contribute unless total lift off pedal. Anyone learning a manual tranny has experienced this. My 2nd car is a 2012 Grandsport vette with stick. The solution when this occurs in the vette is to quickly depress the clutch. Has anyone tried to pull the right paddle with light throttle to calm it down? Generally my MB 9 speed trans seems all locked up like a clutch trans too much of the time.
I've also noticed it doesn't like the gas pedal to be stomped on. Ease in and it rockets off. Wack it in 1st or 2nd and it just denies any real go. Haven't tried turning off traction control.
And yes the auto start thing is annoying and the first thing I disable. again and again and again...
I have had my car to the dealership three times(in shop for 6 weeks last time)with no positive answer to the problem as described in all the other posts.
The dealership have been speaking with MB Technicians and have had no success in solving the problem.
I feel that I would like to hand the car back to MB for a refund as the problem totally spoils an otherwise superb car.
It's a GLC43 but on their paperwork they have it down as a GLC300 in case it confuses anyone
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I've got this issue as well. I'm on my 2nd visit to the dealer trying to get this addressed. I sent them copies of of ajgrahams invoice (see images above), pointed out the bulletin number (LI27.00-P060741) and asked them to install the associated update.
Result so far? They didn't install the update. (They said it was for GLCs with 4-cylinder engines.) They've asked me to describe when the problem occurs which I've done but they refuse to let me ride with a tech to show them. They've asked me to keep the car overnight.
**fingers crossed**
Last edited by FrostyZoob; 08-15-2018 at 02:57 PM.
Sorry to hear you're having the issue as well. It's interesting what they said about that bulletin as the problem seemed to recede but it's still there so they might well be right and my dealer was lying (which would not surprise me at all), I think the clutch and gearbox adaptions smoothed out some of the jerkiness I was having but the core problem is still there. In one of the earlier threads OMSE mentioned about the low voltage error which we both had and is perhaps the cause. I've not looked into that as my dealer really is terrible and after my rear suspension failed at 12k miles I decided I was done with the car.
If I was in your shoes I would email the head of servicing of the dealer and explain the issues, that it's reproducible and ask when he next has 5 minutes so you can show them. If you have other Mercedes dealers near you could try going in to speak to one of the senior managers and see if they're more cooperative. The problem I find having dealt with numerous service people is they don't care whether the issue is resolved, they're happy to get the technician to do the bare minimum and tell you it's fixed so finding the right manager to oversee the process is critical. Getting them to check fault codes for the low-voltage error seems to be the only commonality found so far.
I'm due to collect my BMW X5M in the next week but I'd be interested in hearing what happens with this and contributing where ever possible.
02-03-2018, 05:24 PM
. Not sure exactly what I did to make it stop, but I think I took my foot off the gas completely, slowed down, and then slowly pushed back on the gas pedal. Couldn't do anything too crazy as there was a car fairly close behind. Tried to replicate on the next turn and didn't happen, but I think I almost came to more of a complete stop versus the "bucking" turn where I had a little speed. Off to try and replicate again and then an appointment with the dealer. Crazy...
