ergon

It goes like this. Pull up a incline, stop, place it in reverse and roll back, stop, place it in drive, release your foot from the brake and the car will continue to roll backwards with it in drive. Now WTH is up with that? First time in my 63 years I've had this occur with any auto trans, but then again I'm not a auto fan (this is for the wife) and things like this are part of the reason. If anyone has any advise or knows of a service bulletin please advise. It's a 2010 Sport.

kevink2

No problem, just one feature not included.

You can have the 40-60 year old slush boxes that have hill hold. This new MB 7-speed ATX is state of the art, with perhaps one flaw they likely could not avoid based on timing and cost.

This is the only atx trans I know that has serious high-torque Torque Converter Lock (TCL) in all 7 gears as the default mode, thanks to a heavy duty TC clutch with muti plates. When the trans shifts, you quickly engage the next gear in TCL mode, ie like an auto shift manual trans (audi DSG and BMW SMG come to mind.)

MB 7-speed atx description ---> about 1/2 way down

Trans Sectional Image ---> note beefy clutch in TC

From what I read, MB avoided new crash test requirements on the 722.9 7-speed by more or less staying with the same case envelope of the prior 5 speed 722.6, and avoiding changeing the trans tunnel. In the process, there was not room for the old sprag type hold mechanism.

Evolution of the 722.9 7-speed automatic

Per this link, some have hill holding capability if you use the brake first. Remember that new flushed trans fluid is required every 40K miles.

.

RLE

I'm not understanding why you are putting it into reverse after stopping but I can tell you that my C300's Hill Start Assist holds the brakes just long enough, about two seconds, to move your foot to the gas pedal. The transmission has nothing to do with it except that it needs to be engaged, I suppose. I think I'll test that tomorrow.

BTW, my C300 is my eighth MB, all automatics including the previous five-speed, and none had this feature.

Your 1947 Studebaker did indeed have a hillholder which was entirely different.

ergon

Thanks so much for the information it was most helpful.

Erich

ergon

"I'm not understand"............how about "don't". I did have a 53 Stud coupe 327/365 Chevy with a m22. I sure as hell miss my 522 RWHP/498 Ft lb Torque Cobra. My Nitto 05R's 325x35x17's held very well on hills but much better on 1320'. Ask the last three Z06's I laid to waste. This thing (C300 Sport) couldn't pull a greasy string out of a cats anus or out run a Moped. It looks nice handles fair and rides well. That's about all I can say. If I had the money I would have the Brabus 4.0 work done.

Carsy

Another satisfied Benz customer !! I wonder when folks stoped taking test drives before buying ?

ergon

I DID, MY WIFE WANTED IT.

Carsy

Between a rock & a hard place then .

Acapulco Bill

ergon, a read-through of the owners manual is a true fountain of information. Here I have extracted the Hill-start assist system page. FYI.

Note that this has NOTHING to do with the transmission (works the same with either manual or 7G box), and that the moment you release your foot from the brake, you have about a second or a little more to accelerate or gravity will take its toll, backwards. Somebody correct me if I am wrong, but the Yaw sensor comes into play here?

For those with the C250 CGI with the auto-stop and start, this is the same second needed to restart the engine, which also activates when the driver releases the brake pedal. Cute trick!

jimmythegreek

exactly why I got the 3.5, and did some work to it. The 3.0 was rly bad, especially in 4matic. Even w the 3.5 its not much. The 4.0 kit doesnt add enough HP for the 15k price tag, cheaper to trade on a 6.3
I dont understand why noone has come out with a charger for these cars or at least some type of updated turbo/intake system. Theres tons of them out there and everyone would buy one, u can turbo or charge everything but a C classs..........WTF

ergon

Thanks for the info Bill. I'm use to the valve body determining that I have the vehicle in drive and changing the flow thus torque forward. This setup may be great if you're a LEFT foot braker. But, this isn't NASCAR. I'm sorry, but I don't like the idea. A standard on a hill, I can hold with the clutch no brake. Comes from drag racing. That doesn't fit in here.

I'm here to learn. So thanks again,

Acapulco Bill

Originally thought that the Hill-assist wasn´t such a bright idea. Also agree that it is pretty simple to keep the car stable on an upward incline either with an automatic or a standard.

HOWEVER, you have to agree that the Hill-assist scheme is a whole lot more fuel efficient (why use FUEL to provide torque when you are STOPPED anyway, not to mention the wear and tear on the clutch or torque convertor).

If you analyze this situation, the potential energy of the vehicle on an incline, if not held by the brakes, has to be compensated by the equivalent amount of kinetic energy provided by a slipping clutch or a spinning torque converter. That same kinetic energy gets dissipated as heat, either a burning clutch or smoking transmission fluid.

One way to think about is: How much energy would a dozen men provide to hold with a rope, a car stopped on an incline? A STEEP incline? Could an elephant do it? How many horses? Thats how much energy the Hill-assist proposes to provide easier and safer access to.

The incoming European efficiency and emissions standards will require the start-stop technology in order to meet their stringent spec, tell me how are you going to feather the clutch against ZERO RPM´s? The US standard, especially California, isn't far behind anyways.

So give it a try. Gives drivers less to do, surely many objected when the spark advance lever was eliminated from the steering wheel. Many cross streets here in Acapulco have surprising inclines, the local taxi drivers with either manual or automatic transmissions always roll backwards a bit, and some scarily more, in the transition from stopped to forward, at stop signs or traffic lights.

The Hill-assist brake system provides that you always go forward, without wasting energy or wearing out expensive components of your W204, brainlessly I admit, but safely and efficiently.

kevink2

I'm sorry if I misunderstood you, but Bill explained how your car has "hill start assist" provided by the brake system. It's up to you to stop the car on an up-hill condition ... simple matter of holding the brake pedal. When you want to start up the hill again, the system holds the brake on an extra second as your right foot goes back to the gas, to avoid any drift back.

Glyn M Ruck

+1

dcjwlee

How often do you drive up an incline, put it in reverse go down the hill and then back up the hill in drive??? Why???

The only bulletin I've seen pertains to a slow to engage reverse gear.

kevink2

Bad example, answer is Zero energy, just a lot of force, as with the brake hold.

The guys exerting force with rope, is like holding a torque wrench on a wheel nut at 96 ft-lbs .... no work is done (ie force times distance), and no energy is involved.

You are correct about holding rpms up with torque converter, wasted heat energy = the torque applied by the engine x rpm.

.

Acapulco Bill

@kevink2: You are right in saying no "work" is being done. However force is being exerted WITHOUT work being done, and that is inefficient. This force is dissipated through friction as heat. Like a jet rocket being used to keep a door shut, a latch is much simpler.

And so is the Hill-start assist system as opposed to burning a clutch or ruining an auto transmission.

By the way kevink2, how do you like your Luxury suspension with the Sport grill? I should have done that instead of the C300 Sport.