As most of you may know, I had the Renntech ECU and TCU upgrades done about a year ago. During that time, many have asked me how do I like it and I've responded that it is great except that at times I've noticed a thud like shift from 1st gear to 2nd gear on occasions. Well, I was studying the manual about the selection of "S" (standard) mode and the "C" mode. All along I've kept it in the "C" mode. I think this is what has caused the jerky shift as all along it was shifting from 2nd to 3rd, instead of 1st to 2nd.
I think I finally understand what the two modes are:
S mode allows the tranny to start from 1st gear and go on upwards whereas the C mode starts the car off in 2nd gear (I think I'm right about this).
I've noticed the thud has completely ceased now that I keep my selector in S mode. So now I am very pleased with my Renntech upgrade.

However, I have a question that applies to everyone (which is unrelated to the Renntech upgrade). I've noticed that if I am sitting at a stop light while on a slight uphill incline (not applying the brakes) , the car wants to slowly drift back while in the S mode but if I switch it to C , you can feel the car suddenly utilize the tranny to hold the car in place. Now why is that if in C the car is , or should be , in 2nd gear??? I tend to think the 1st gear , while in S mode, would prevent the backwards drifting better than 2nd gear while in C mode. Isn't the car sitting in 2nd gear at a standstill while in the C mode and in 1st gear while in S mode?

 

Re: Question that applies to everyone.

Good question about the transmissions!

I drive in "C" mode an S550 with ABC, thus not 4-Matic, and I am also a bit puzzled about the Comfort/Sport starting gear selection.
Since my car was new about 10 months ago, I have experienced about a dozen times that upon stopping, and driving off, the transmission will not shift out of first gear ( indicating a "1" and "C" on the instrument cluster which contradicts the manual's assertion that the car starts in second gear while in comfort mode ( page 400.)) The tranny can then only be brought back to shift automatically by holding down the right shift paddle until 7 shows on the screen. After that, no problems for a while.
The incidents have always occured after stopping and driving off at a railroad crossing or leaving a parking area and rejoining the road driving over the roadside gutter.

There are few S550 with ABC around here, and the otherwise good mechanics my dealer has, are probably not familiar enough with odd "S" problems to diagnose this type of malfunction with the available electronic diagnosing equipment they have at their disposition.

I have asked the dealer to involve MB to assure a solution to my particular problem.

Our problems may not be identical, trumpet1, but perhaps the roots are.

May we hope that these "non-official" comments eventually trickle through MB's thick bureaucracy, and reach the original designers who are the most in need of user's feed back to recognize that some reprogramming or "whatevers " are in order to correct unforeseen complications in their creations.

 

Trumpet1 you are correct about the `S` and `C` button function,, s you will start off in first gear normal driving mode,, c you start off in second gear it will shift to first if given enough throttle on take off, it is used if snow or low tracktion conditions when you don`t want to spin the wheels,
not sure on your second question will try to find out.

on the 04s430 trans complaint the gear shifter can get hit to the left and that would put the trans in first gear and won`t allow it to up shift,just a thought

 

The letters have different meanings depending on whether you are referring to a 550/600 versus a 65. (I'm getting this on page 383 of our manuals if you want to look for yourself).

On 550/600, the C stands for comfort driving and the S stands for standard driving/shifting.

On 65s: C now stands for standard instead of comfort and the S stands for sporty rather than standard.

Kind of confusing to me.

This switching ability controls the shifting pattern as well as the airmatic suspension response and it also alters the engine performance to some degree in all cars.

C mode: starts out in second gear (both forward and reverse) for gentler starts. It is overridden and will start in 1st gear IF you accelerate very quickly despite the fact that you have selected C.
This is better for slippery/icy conditions. Upshifts occur earlier.

S mode: starts out in 1st gear and upshifts occur later.

All I can say is that if you are unhappy for some reason with shifting while in one position (for me while in C), change to the other position and you may be satisfied with that choice (I seem to prefer S).
According to the manual, it's worded as if we should leave it in S mode for standard shifting. Standard , to me, sounds like wording to suggest "normal" operation.

However, the manual states on page 414 that C mode puts the suspension in the default setting. So, it is rather confusing as to which position is best to stay in for 90% of the driving conditions. Since I drive on rather curvy, stop/start conditions, S is better for me. On the other hand, if I were to do most of my driving on interstates and long stretches, I'd probably choose the C mode for a more cushy ride.

One reason I was confused is because on the MB website under "owners online", the description of the tranny positions (C/M/S) never mentions suspension in the write up....only transmission positions.

 

Correct, on our previous car, my wife would accidently hit the shifter to the left while at a red light or whatever, and the car would shift down. Can't remember exactly, but not necessary into first.

However with the S550, I would have to be in Sport mode and activate ( and hold down,) the left paddle on the steering wheel to get into first while stopped. I always drive in C, and I do not touch the down shift paddle. It happens on its own!

 

Now I'm puzzled. I'm in a rental 2006 C class as my 2007 S600 is in the shop today for the idler pulley replacement and this morning I noticed the exact opposite occurs while in the C class car. The S mode holds the car on an upward slope while at a stop light whereas after I shifted it into C, the car drifts (which is actually what I thought it should do in my S class car).

It almost makes me wonder if the Renntech guys have my S and C mode switch programmed backwards?!?!

Completely opposite of what the S class does.

 

Have always driven in S mode, except when raining/wet. Prefer shift patterns/throttle response/tighter ABC of S mode....

Sit on many steep uphill lts in SF, so am accustomed to being decisive re: application of brakes.....Is your car's HillStart function working properly?....do notice that S/CL (in either S/C mode....whether 550/600/63) tend to roll back a bit on inclines if one doesn't engage HillStart....and/or decisively move from brake to throttle on inclines....

 

Spent a coupe of hours at the dealership this morning. Tranny problem solved!

 

What did they do or change?? Software upgrade?

 

I wish you had not asked!
The dealer's shop foreman rode with me for a while to see if we could duplicate the problem. It happened, but he observed that the way I held the steering wheel, after a stop and making a turn, could be the problem.
We tried it again, and sure enough, my hand somehow came in contact with the downshifter.
Very, very embarassing. After nearly sixty years of driving, I am the one that needs an upgrade.

 

Don't have 60 years of driving experience, but hope I will reach that. I've been wondering if I let wife go alone with the car and she hits the downshift button, would she realise what's wrong.

Anyway, points to the MB dealer this time, great that the issue got solved.

 

Are MB shift paddles simply extensions of the shift buttons or are they fixed paddles that extend off of the steering column? I have always disliked paddles/buttons that are non-fixed because you lose perspective as to where they are if you're in a big turn. True paddles should not be attached to the steering wheel but should extend out of a hole within the steering column? I've never really taken a close look at a benz with paddles.

 

Unless she has read the operators manual, it could very well happen. Avoid the problem by telling her what to do.
( There will be a good bottle of wine on its way for the dealer's shop foreman. )

 

They do not extend from the column but rather seem to be extensions of the buttons on the back of the wheel.

 

That's what I thought.

 

The shift paddles are located on the back of the steering wheel's spokes, just in a few centimeters so that the fingers can reach them. Had they NOT been attached to the steering wheel as you suggest, I could have saved myself the problem.
I am surprised that this has not happened to anyone else.
Anyway, I am happy there was a simple solution to what I thought was a defect with my car's transmission.

 

It has! I've done it with my buttons but I eventually figured out what I did. Trivial but true.