JimGnitecki

I realize that MB programmed the C63 to start out from a standing start in 2nd gear when in Comfort mode. I also realize that MB probably did this to make the driving experience in Comfort mode smoother and quieter - after all, it IS called "Comfort" mode.

But, is it harder on the clutch plates in the clutch (versus torque converter) equipped transmission?

I ask this because the difference in gear ratios between 1st and 2nd gear is a big one. When manually shifted, 1st gear will get you to about 42 mph. 2nd gear will get you to about 64 mph.

In general, 1st gear in a manual tranny in a typical performance car is good to anywhere from 40 to 50 mph, except for a number of European cars that take 1st up to 60 mph because they are high speed versus drag race oriented, and need the "taller" 1st gear to keep the gaps between gears short enough to support the use of peaky high rpm engines.

Going to 64 mph before shifting means that the period during which the clutch is being "slipped' is longer. This is because on a typical enginewith manual transmssion, the clutch HAS to slip until the engine rpm is high enough to make sufficient torque to enable a no-slip full connection. A typical automatic transmission with its torque converter does not need to "lock up" to propel a car - the torque converter is deliberately designed to work with "slip" when there is a large difference between engine rpm and road speed.

If you've ever tried starting out from a dead stop in 2nd gear with a manual transmission, you know how much longer you have to slip the clutch before you can fully engage it. And what ultimately wears out a clutch is the amount of time it has spent in slip mode, and how much torque has been applied to it while in slip mode. For this reason, I have always viewed a 2nd gear start as abusive, and only to be used on ice or snow when there is a traction problem.

So, in theory at least, starting out in 2nd gear in the clutch (versus torque converter) version of our tranny, "should" wear out the clutch pack sooner. But obviously, MB does not think it will wear out "prematurely", since it programs this mode of operation into the C63.

But that is all theory. In practice, have C63 owners on the forum, who drive a lot in Comfort mode, experienced clutch wear or not? Obviously, I'm not asking anyone who tracks his car , or who likes to do jackrabbit starts, because both of those habits will of course wear a clutch pack more quickly. But have C63 drivers who are conservative and who drive a lot in Comfort mode actually experienced discernable clutch wear?

In terms of symptoms, I would expect premature wear to manifest first as flaring during shifts, and later as obvious slip.

Any comments?

Am I way off base here, or ?

Jim G

604 C63

Done and done.

BLKROKT

/thread

Of course it's not bad in any way

NotABaller

I don't own a c63 yet but to reduce clutch wear, I always shift my WRX to neutral so I can get behind the car and push it to a rolling speed before hopping back in and taking off in 1st gear. Not recommended for up hill launches due to physics reasons.

JimGnitecki

Good one.

Would it be easier to just wait for the car driver behind you to get impatient and PUSH you?

Jim G

NotABaller

If by push you meant punch then yeah that actually tends to happen a lot

Jasonoff

This is obviously a troll thread...

NotABaller

OP is clearly correct though. Theoretically, it would wear the parts more to start the engine and drive away in second gear. I think the real question is, does it matter enough, even over a long span say 10 years?

I think the answer is we don't know yet.

PeterUbers

We do know

Comfort mode has been around for quite a while with Benz V-8 engines, and it does not seem that there are excessive transmission failure is beyond what we statistically expect for this brand.

NotABaller

If previous transmissions also started the car in 2nd with no durability issues then I guess that settles it.

BLKROKT

JimGnitecki

No, I asked it as a legit question. It just seems weird to me to start a 4000 lb vehicle rolling with a gear that tops out at 64 mph. But, if there have been no premature clutch failures in so many years of that programming being in use, I guess it is not a problem.

I personally prefer the "S" mode in the C63, but my wife loves the "Comfort" mode.

Jim G

Jasonoff

You have the MCT so...

Final drive 3.06
1st gear 4.38
2nd gear 2.86

You have more than enough torque in 2nd to get going without any unnecessary clutch slippage.

If you mash the throttle, it will automatically downshift for you.

Alex.currie44

If you read the link I just posted you get an overview of the evolution and application of the 7G trans in torque coverter and MCT forms.
It is all about fuel economy for the most part. In theory, a second gear start is better in the wet and in snow. The dual reverse is there for the same reasons.
I have had the 7G TC model in a W211, a W212 both 4Matics, and SLK350 with no issues and they all start in 2nd gear in C or Economy as they called it.
I do know from sad exoerience over this past winter that with the wrong winter tire 2nd gear or option reverse gear selected by the system matters bugger all. There is s much power that on our wet snow it is very iffy if you will go anywhere at times.

JimGnitecki

Yes, Alex, I just saw your post on the other thread, and responded. My theory is that after MB realized that the "winter" mode is not harmful to the tranny in the long-term, they "rebranded" "Winter mode" into "Comfort mode" to satisfy customers who don't like the jerky starts sometimes experienced in "S" mode.

Jim G

Alex.currie44

The 7G has been around for 14 years and the MCT since 2005 and you just don't read about clutch issues.
On the other hand if you go to the W211 forum you will find instances of transmission failure but not due to the basic transmission. In the 4Matics there was a period wherein there was a faulty bearing issue in the transfer case and being an open unit when that bearing went it took out the transmission at about a $10K CDN cost.
As is typical a lot of US owners got their transmissions replaced even if they were out of warranty. Merecedes Benz Canada would not even acknowledge they were aware of the issue and if your car was out of warranty so sad, too bad. Hence my first EW.

Alex.currie44

Actually having had 11 of these cars and driven a number on the autobans in Germany, I have seen all sorts of labels for this same feature depending on country, model, year of model etc. It is marketing and not much more.

JimGnitecki

Sorry to hear that, Alex. Was that MB-Canada handling of the situation isolated to that issue, or does MB Canada in general take a less helpful stance than MB USA on warranty issues?

Jim G

JimGnitecki

This too is interesting, because labeling the feature as "Winter" implies that you should not use it in "normal" conditions, whereas labeling it as "Comfort" implies that you should go ahead and use it if you want a smoother start from a dead stop, and prefer to drive the car like that all the time (like my wife does).

Jim G

Alex.currie44

First of all I did not experience the failure. When MBC was contacted by me about it I got shuffled off as usual. We do not have the consumer laws in Canada that the US has so MBC just basically tells you to **** off. Hnece I bought my first SD EW
My 2001 CLK 320 had a metameric colour match between the door panels and lower IP which was hugely visible on dull days with windows closed. Most would perhaps not see it but since I was in the interior cover stock business and this being a first test of any new colour match I spotted it right off.
They offered my dealer warranty replacements but if they were no better then the dealer was hooped for the cost.
When the M112 V6 first came out there was a design fault in the upper galleries and oil was not draining back to the pan so coking became a problem in the oil passages of upper chambers of the engine,blockages occured and engines failed prematurely. MBUSA extended the engine warranty on all cars up to a particular engine number to any owner of a car up to 10 yr from ISD. MBC. No answer to two letters to the then president of MBC nor from Stuttgart. The CLK320 had that engine and it went away.
My 2003 E320 had the same engine and one day I got noticed my oil had been changed to synthetic. I finally got my hands on a service bulletin and they were still concerned about the issue they never publicallt acknowledged in Canada, The M113 was the V8 version of the same achitecture but I never heard of the issue in those engines so they must have worked it out before hand,

Alex.currie44

One more point and I am done on this one. There is a vast difference in the starts in 1st in these cars than I ever experienced in the E's, the SLK and even the CLA45 AMG with its puny 2L putting out 355 hp. Jerky starts is a very relative term when comparing them in this car in 1st to those others in 1st. Trust me,

JimGnitecki

Just to clarify, Alex, is the jerky start in the C63 notably better or notably worse than the other models?

I'm asking because on my car first gear starts in "S" are not a "problem", although the 2nd gear starts in Comfort are notably smoother.

Jim G

604 C63

I had no idea what that word meant. So I looked it up. I get it, but I had to really think about before it sunk in.
Maybe my mind is mush from the guys in the row in front of us at U2 tonight hitting the BC green continuously for a couple hours. All I know is I really want some cookies.

Thanks for the new word though.

Vladds

The gearbox is a torque multiplication mechanism.
The torque at the wheels that people see on dyno sheets is not the torque at the wheels, but only a number used for comparison.
The torque at the rear axle is found by multiplying the engine shaft torque by the gear ratio and the final drive (in a regular manual transmission).


At "the wheels", more accurately, at the tire contact patch, there is no torque, but a tractive force.


With this said:


The process of putting a manual car in motion is rising the RPM, with the accelerator, so that you get a bit more than idle torque, then clutch out, where the clutch disc slips, so that the torque can be transmitted gradually to the wheels and put the car in motion smoothly.


In first gear, due to the large multiplication, if you were to let the clutch go fast (dump it), you could avoid spinning the clutch disc, but spin the wheels instead.


Now in second gear, with a much reduced multiplication, you can dump the clutch and all you would get is just almost smooth engagement, so no clutch slipping. So less clutch wear. So you're fine.

brad65ford

Which tran 7g or MTC? Can only relate this subject to slipping clutches which you can focus on guys that are supercharging theirs. These are the guys slipping/damaging clutches, not related imo but most do start out in 2nd since there is a lot more torque when you have a roots style blower. There is talk about which trans is stronger for supercharging but not much regarding stock power reliability. Won't worry about starting out in 1 or 2nd especially if you N/A though, unless you have nothing else to talk about.