Ben'sBenz

+1 on meeting the SA in the morning.

rb23lb

So I listened to your guy's advice this morning and sat in the car with the mechanic and took up from cold start and sure enough, there was the sound!

Hit right about 18 mph when the faint clank noise sounded off from what seems to be the front driver's side of my car...

The mechanic heard it, but after discussing with me that it was such a light ping noise and that from his knowledge was nothing he has ever heard, said that there was basically nothing they could do.

He told me they already went through all the standard checks of my suspension and bushings and that they found nothing out of the ordinary.

GREAT.

So my warranty is up on the 27th and I hope it doesn't lead to anything else more serious.

Please somebody post if you are able to get this resolved.



BTW, this was at Beverly Hills Mercedes Benz Dealership

rb23lb

On another note, I left my car there for the day and had them Upgrade my transmission software to the latest 2012 version

After driving the rental c300 with more miles than my car and feeling like it was faster than my C350, I told them I needed the upgrade to see if it makes a difference.

The rental felt like it had a powerchip or a frickin sprint booster

We will see what the new software upgrade feels like tomorrow

jctevere

I actually think that this noise might be normal... I will check it out in the 2011 w204 (same c300 4matic) when I get a chance and see if it does it. HOWEVER, I will note that occasionally, if this spring sound doesn't happen BEFORE the shift into third (around 15-18mph) and happens AT the shift (around 20mph) like mine sometimes does, it causes a "rougher" shift and a noticeable throttle in the rpm's. THIS I don't think is "normal"...

EDIT:

Also, I found an earlier thread somewhat related to my rough shift: https://mbworld.org/forums/c63-amg-w...x-problem.html

They also talk about this issue from 2nd into 3rd (and when downshifting from 2nd into 1st - only is done in sport mode) being rough and somewhat lags...

Apparently there is a TSB on this issue: "There have been issues with the 7G Tronic but primarily on non-AMG models. The issues are abrupt shifts from second to first (in S mode) and the 2 to 3rd gear hard (slow) shifts.

The fix has been a valve body replacement. You might want to do a search here; I think there are a few TSBs out on this."

Glyn M Ruck

The latest 722.9 flash does not change to first until the vehicle comes to a dead stop when pulling up.

Ben'sBenz

So because he doesn't know what it is, there is nothing they can do? That's discouraging. You would think they could consult MB to try and determine a cause before just giving up. Originally mine was doing it every morning, but now it's much more frequent. If the car sits for just a couple of hours it happens.

dcjwlee

rb23lb

When I was taking the rental back this morning, when I left my house I heard it for the first time make the same clank noise that my car does...

so I guess this is pretty common issue and maybe normal and probably most people just dont hear it...

the rental was a 2010 c300 with 29000 miles

my car is a 2008 c350 with 26000 miles


both make the same noise I have now determined

rb23lb

I just got this Flash, and can agree that it seems to not "clunk" back to first in sport mode anymore btw, they also checked my tranny fluid and it was "normal"

Now I have a question... Is my car "permanently" upgraded to the latest Tranny software? meaning, is it stored in a different location than an ECU tune would be?

reason being is that if I ever get a POWERCHIP tune, will it overwrite my factory software permanently ? or is a completely separate deal?

Petje

Yes your tranny has his own computer! So they only flashed you tcu , and with a powrchip they do your ECU

rb23lb

checkout the new shift points that they set with the new TCU

so why is the ECU necessary and how does the ECU interact with the TCU? Don't they do the same thing basically?

Glyn M Ruck

+1 The flash for transmission control is only on the TCU EPROM

The ECU controls all engine functions. The TCU & ECU however work in conjunction with one another. As an example the ECU retards timing at the point that the TCU signals a gear change to smooth out the transition.

MB_C300

I have same noise exactly as you describe it. My car is C300 2012 and has only 3000 miles on it... I notice the noise when my car hit 1500 Miles I took it back to my dealer 3 times and they didn't find anything.. please if anyone solve this issue, share it with us....The noise is driving me crazy as I hear it every morning when cold engine.. The noise sometimes very high and sometimes very low. It happen around 18 MPH when slow acceleration...Please Help

jctevere

I have had this issue on all 4 C/W204 models we have had. If you look above at my post 29 it describes the noise.

On the 2008/2011 c300 4matic sedans and on both of my 2012 c250 coupes. The 2012 have a revised transmission and it doesn't do it as noticeably/rough, however, it still has the same issue.

I think this is a design flaw and I have not had any mechanical issues yet (over 60k on the 2008. Since the 7 speed is not symmetric, I believe it has to depressurize one gear "pair" to pressurize another. The first time this happens it is rough, but after it seems fine.

I lease all my cars so I don't care too much. If you own, try raising Te issue with MBUSA. If you don't get anywhere I will try to escalate on your behalf to my contacts at MBUSA.

MB_C300

Thanks jctevere for your prompt response, I own the 2012 C300 4matic and I am the first owner... I am sure there is no rough changing gear, it is only the clunk spring like noise, sometimes it is right when first gear change occur and never happen again till I park for few hrs. I noticed also sometimes it happen right before first gear change, again no rough change at all only the clunk noise....

Again thanks for you help, if you have time, please do so and raise one on my behave as I am new to MB world or point me there.

Acapulco Bill

The clunky shifting from 1st to 2nd gear is an inherent design flaw of the 7G Tronic. In first gear, brake plate B3 is activated. When the TCU commands the shift, the valve bodies release B3 and transfers pressure to brake B1, inside the same planetary section. See attached graphics.

This requires a huge rotational deceleration of the outer planetary gears (the ratio drops from 4.377 to 2.859, for example from 5500 RPM to 3600 RPM). Although these rings and gears are helically cut, there is always some backlash. There is also a variable intentional shift delay built into the TCU programming from 0.5 to 1.53 seconds in the transfer of full pressure between the plate sets, with the intent to smooth the transfer of revolution and torque, necessary because of the 7G's weak engineering. Even so, the centrifugal kinetic energy of the system has to be absorbed between dissipation of heat by the brake plates (friction) and mechanical movement (sound and gear wear). Result: a clunk, especially when the transmission is cold.

Shifts between 3rd, 4th and 5th go more smoothly. One would expect another irregularity between 6th and 7th, however the small difference in ratio change (less than 13%) results in a practically imperceptible shift.

The whole result of this design is an inferior, fragile transmission that is reviewed unanimously in the automotive press as being slow and lethargic. Originally designed to provide an ATF "lifetime filling", the 7G Tronic is a disgrace, burdening the owner with constant and costly service, refills, and in many cases, failures. BMW and ZF provide quality, sophisticated automated manuals. "lifetime ATF fluid fills" and with shift times measuring in milliseconds, not full seconds as intentionally programmed in the 7G.

Hopefully MB has engineered the upcoming DCT with more intelligence and robustness. For now, Mercedes Benz owners with the 7G Tronic must suffer these inherent deficiencies for the lifetime of their ownership.

MB_C300

Do you think my transmission will fail after certain time/mileage due to this defect...I am really worry now...I mean I can live and try to adapt to this clunking noise as long as the transmission won't fail. Please Advice

Acapulco Bill

The 5G Tronic 722.681 5-speed automatic which is in my 2006 316CDI MB Sprinter, under extreme loading conditions totaling 10,200 GVW (1650 lbs over limit), has lasted 322,611 kms (200,000+ miles) with just the scheduled fluid and filter changes. See photo of speedo.

There are three capacity variants of the 7G Tronic, 400 Nm (up to the 3.5L gasoline and 3.0L CDI), 700 Nm, and more recently 1000 Nm used in AMG and V12 models, the 5G being installed for some years in the AMG and V12's after the 7G was introduced. Some engines even had their ECU's torque-limited to prevent destruction of the 700 Nm 7G. With the introduction of the 1000 Nm 7G, capacity is now adequate, although even in the C63, CLS63 and E63 reviewers say the transmission is rubbish (except for the Black series which has a different configuration).

That said, under conservative driving, the 7G seems to be reliable, however few have reached the 100k mile mark to get a proper statistical sample. In contrast, the ZF in my exotic V12 under constantly extreme driving has logged more than 120k miles with no service, in Sport mode the performance is genuinely frightening.

A major change in design from the 5G 722.6 to the 7G 722.9 was, instead of having all double-sided multi-disk friction brakes and clutches, in the 7G only the B2 and BR (reverse) brake disks are double-sided, the other 5 sets are now single-sided. This transfers torque less efficiently (i.e. with more slippage and less damage to internal components), and causes less stress on gears and bearings.

The price paid for this "reliability" is performance. The equivalent-engined BMW 3 series is a full second or more quicker than the W204, just because of the 7G. A blatant example is the 2010 C300 which boasts 10% more HP and 14% more torque than the 2010 3.0L BMW 328i, however the BMW is more than a full second faster 0 to 60 MPH.

One wonders why MB_300C insists in driving in Sport mode (eliminating the 1st to 2nd shift, unless fully floored in "C" Mode)? This practice causes higher engine revs, meaning more wear-and-tear through slippage of brake and clutch friction disks, and it has yet to be demonstrated that "S" provides faster acceleration that "C" or "E" mode (please correct if this is wrong). This spirited driver prefers "C" or "M" mode, saving "S" mode for vehicles which are designed and actually provide benefits in real performance, such as my V12 or M3, besides durability.

OCDBenz

My C300 does the exact same thing. My Nissan Altima Coupe did it, as did my BMW 328i. I brought my Bimmer in and they knew exactly what it was (supposedly). They said the traction/stability control does a "self check" at 18 MPH. You hear it/feel it more when the car is cold because the RPMs are just a little higher when the car is cold. Sounded okay to me. Thoughts?

Glyn M Ruck

The 7G is not an inherently weak transmission. Benz never claimed filled for life. MB NA did that. Due to number of changes in the 7G it actually stresses the fluid charge to a greater degree than the 5G. The only common problem with the tranny was the Siemens conductor plate which resulted in a much acrimony between Benz & Siemens. We have many of these transmissions in South Africa's harsh conditions with over 500K Km's on them but serviced every 60K Kms as mandated by Benz Germany from the outset.

Remember from approx August 2010 production we are talking about the 722.9 Plus. The design fluid change interval with the 236.15 fluid is 120,000Kms. We will see how that works out.

I have never heard the transmission itself clunk. Only the axle as a result of behaviour with the old software flash due to the huge ratio change & catching out the TC clutch lock-up or release under certain conditions. Something the 5G could also be induced to due usually as a result of clumsy driving. Once again the 5G was taking up lash in the axle.

The Torque rating of the transmission is appropriate for engines it is coupled with. Software used with high torque diesels is appropriate for torque. (e.g. you can't force a 2nd gear pull away at high throttle input)

The 722.9 in my CLK is utterly smooth on all gear changes both up & down.

The major cause of mechanical failure of these transmission has been a lack of servicing at the required 60K Kms or 39K miles. We have thousands of oil samples from these transmissions & they require their 60K Km filter & fluid change. Especially if driven hard or used for towing. North America caused it's own problems with the transmission by violating the ROW service mandate.

There is never any uncontrolled slip in these transmissions with the correct fluid.

Glyn M Ruck

BTW ~ In side by side dyno testing of the BMW 2013 DCT transmission vs the 7G Plus the Benz transmission is the more efficient of the two by quite a wide margin on power loss from flywheel to back wheels. In a recent test I was involved in the transmission loss to wheels was 16.5% for the BMW while the Benz loss was 11.9%.

2013 BMW M5 vs 2013 E63 AMG.

Acapulco Bill

Thanks for the great information, Glyn. Attached is a page from the original MB service training manual to update procedures from 5G to 7G for service mechanics. When first introduced, the 7G was touted as having a lifetime fill. However MB soon changed the service to every 60k kms. Unfortunately the 7G casing, still makes servicing difficult and arbitrary as to the exact final level.

If the 7G was truly designed to be regularly serviced with ease, why is the refill procedure so Byzantine? Maybe MB copied the original VW Beetle transmission filling process of pumping lubricant into the side mounted filler plug (not the drain plug located on the bottom) until the casing overflowed, wait until the flow slowed so that the oil was 3 mm above the level of the hole, then quickly shove in the plug to stop the dripping and tighten.

But a thermometer for the 7G refill? Isnt that a bit... rectal?

Glyn M Ruck

Yes ~ That was the US training course. I have personally delivered the global one & have a copy.

The service procedure was meant to keep Benz dealers in business hence. (see pic)

All Benz automatics have required filling at a specific temp including the 722.6 ~ 5 speed. Easy if you have a Star connected.

Acapulco Bill

Being an industrial lubricant fanatic (having to stock more than 27 grades of oils and hydraulic fluids to keep multi-million dollar printing presses and cutters productive, a real challenge in Mexico), I am truly appreciative of the value of periodical ATF changes. As Glyn points out, an auto dealer's long-term "business" is not the sale of the vehicle, but its service. It is disappointing that many (most?) MB dealers are just not up to the task, nor will they ever be, as agency owners are investors and bean-counters who have no real passion for fine vehicles that need quality care. But this is off-point.

The 7G Tronic's design mandate apparently had two cardinal requirements: smoothness and fuel-economy. Also high on the list was low weight and "survivability", which is quite different from reliability. Not so important were quick shifting times, robustness and sportiness. It is certain that a large percentage of Mercedes owners with the 7G have never, ever used 1st gear. Basically the 7G is a six-speed transmission with a low-low 1st gear thrown in as an afterthought, like a manual truck transmission.

Further insight into the "survivability" requirement, besides the intentional programming of up to 1.5 seconds between applying full (98%) pressure between plate sets, is afforded by the parameters of the Adaptive Learning algorithm, which records the internal torque at the shifting point, and uses this, averaged, as part of the lookup table used to decide when this action occurs.

Over time, MB argues that Adaptive Learning will retain a higher average torque value for aggressive drivers, and a lower average torque for conservative ones. However, even the most aggressive driver will have their average torque value severely lowered, and therefore have shift points deteriorated, backing out of his driveway or driving in congested traffic. What is the point of having Adaptive Learning at all?

So the 1st to 2nd shift will always be non-optimal, there will be a high probability for aggressive drivers, with a higher torque stored by Adaptive Learning, to experience a more abrupt change, and conservative drivers will probably never notice this design compromise, probably they don't even use "S" mode anyway.

One can only hope that the future DCT transmissions can be authoritatively commanded by the enthusiastic driver, instead of the 7G Tronic's intentional characteristic of being filled with, and therefore behave, as "slow as molasses".

Acapulco Bill

Sorry, it would be shortsighted to not include "wide range of application" as the highest priority of a transmission's design. The 5G certainly survived unforeseen usage quite admirably. Historically, the Chrysler TorqueFlite transmission, starting with the mid 1950's 3-speed, set the industry standard in design, performance and reliability. After more than 50 years, uncountable thousands of these transmissions still function without overhaul or repair in muscle cars, station wagons and trucks with I6 or V8 engines ranging from 5.2L to 7.2L. Still have a 1966 Imperial with a 7.2L engine, the TorqueFlite has never been repaired other than an occasional ATF change, and shifts like a champion. The mileage is astronomical.