Transmission "Clank" Sound...
 

Every morning when I leave my driveway, I start down the street. When my car get's going fast enough to shift from first to second, I hear a pretty noticable "metallic clank" sound. It only happens the first time shifting into second. And only with the engine/transmission is cool. Does anyone else have anything similar to that going on? Any ideas on what might be the issue? Thanks,
Ben

I HAVE THIS EXACT SAME NOISE and ISSUE!
 

This only happens in the morning...

This only happens right about when it shifts into second gear...

It only happens when the car is cold and I leave for work in the morning, probably about 3-5 seconds after I pull away slowly (ie 2nd gear)

You hit the nail on the head...

I thought about bringing it into the dealer, as I only have 22 days left on my warranty...

But figured I would get the dreaded "could not duplicate"

Does anybody think this is a serious problem that should really be focused on?

I thought it wasnt a big deal so I have ignored it, although if I knew how to pinpoint it I would definitely like it fixed....

:nix::nix::nix::nix::nix:

I don't know if it is a clank. I would describe it more as a metal spring unloading or something. However, I'm not so sure that its related to cold starts. I just think that I always hear this noise everytime my car FIRST shifts out of first and into second. Because if I come to a complete stop right after and the car is still cold (literally less than 30 seconds after starting) I don't hear the noise again.

My logic is it is some type of safety spring or solenoid releasing.

Ya not really a clank - more a spring or a metallic "click"
 

I agree- less of a clank and more of a click... only happens first time from 1st to second, :nonono:

When I was writing the post I almost described it as a spring release sound. That's a perfect description of the problem. I can't believe it's normal because it sounds too strange. I thought about taking it to the dealer and having them keep it overnight and try it first thing in the morning. I figured they would give the good ol "that's normal" BS.

I have this same issue in my 2011E 350 bluetec. I have already gone down the road of interacting with my dealer and a regional rep, both whom told me "it's within spec". my car stayed in low gear until I hit 30, the it would "plunk" into second gear. Also had the mystery of having my car indicate I was in "D", but it would not go anywhere. Dealer fixed this once, has happened 3 times since. I am going to '12 model with new transmission

I would imagine that this sound is created from the main pump operated by the fluid coupling/torque converter. The pressure coming from this pump is regulated and used to run a network of spring-loaded valves, check balls and servo pistons. The valves use the pump pressure and the pressure from a centrifugal governor on the output side (as well as hydraulic signals from the range selector valves and the throttle valve or modulator) to control which ratio is selected on the gearset; as the vehicle and engine change speed, the difference between the pressures changes, causing different sets of valves to open and close. The hydraulic pressure controlled by these valves drives the various clutch and brake band actuators, thereby controlling the operation of the planetary gearset to select the optimum gear ratio for the current operating conditions.

I think that this valve opens up when shifting out of first, to maybe get more fluid going, which would explain why I only hear this noise after the first shift after startup, and not every time after shifting out of first.

jctevere, that's one hell of a guess. :bow:

Good reasoning, jctevere, and atx explanation. Not sure I fully agree as the fluid is still heavy/thick for more than a few minutes after a cold start, so I don't see how it explains the 1 clank condition. Shift characteristics are also a function of a bank of electro mechanical solenoid valves, one of which may be getting sticky for 1st operation.

Does it happen in both comfort (2nd gear start?) and sport trans settings?

One workaround would be to use manual mode for 1st shift, either short shifting or letting it rev with light load. Have same clunk on another car on just the 1st shift from 2nd to 3rd. I usually go light throttle just before the shift, or use manual mode to assure light loading between 2n and 3rd on that 1st shift ... no clang/clunck.

ps, jctevere would you please answer my Q's in the "winter tire .." thread? Thanx

.

These cars all suffer some lash in the rear axle assembly that can clonk slightly on a poor gear change. Usually shows under braking hard coming up to a halt as the TC clutches disengage & the transmission changes to first. Latest 722.9 transmission flash halts in second gear & then selects first to obviate this.

At cold start these vehicles go onto high idle & hold low gears longer to heat the cats. This can lead to a slightly harsh changeup until warm. If your rear axle is is built to the "loose" end of the spec it will clonk.

Another thing to check is the rear transmission mount. They fail more often than I would like.

good info
 

good information Glyn! Did you get the new transmission flash to your car? and was it a difference maker that you could obviously tell??

covered under warranty?

I still drive a 203. The lady of the home drives the 204 & yes it has the latest flash & it's fine & you can feel the difference. Requested & done free under motorplan here.

I still don't think this should be classified as a "clunk" as much as it sounds like a spring loaded valve opening/closing, etc. It definitely comes from either the front of the vehicle in the engine bay, or in the transmission area, but definitely NOT the rear... I will pay more attention to if this does it ALL the time on cold startup, and if on both sport or comfort.

As far as the noise only occurring upon first shift, this could be explained by the valve simply opening, and staying open. I think that this same noise is also heard after 2 minutes of the car being shut-off (although the sound is more spread out, and slower). This could be the valve closing?

Those shut down noises you hear on the drivers side in a US car is all the auxilliary stuff shutting down. Excess air pump, Auxilliary cooling pump, Bix self levelling if fitted, ABS pump etc etc.

So it's a noise, with nothing felt?

Ben & rb need to identify which area the noise is coming from on their cars. The propshaft spline can also clonk a little if under greased if it is what I describe above.

A friend who lives on the hillside like me used to get a clonk/clunk/clank ever morning after reversing down a steep driveway & over a chassis twisting gutter into the road below. He used to experience a clunk every morning after doing this and that was the rear tranny mount.

As best I can tell, it's coming from the transmission area. I don't know how to pinpoint the exact location. The sound is front and center. If you suspect it's the transmission mount, i'll mention that to my SA the next time I take it in for service.

That sounds like rear transmission (rear engine mount in Benz speak) mount. (can also be spline, UJ or front flex disc on propshaft)

Yeah, I don't feel anything, its more like a quick spring release. Perhaps mine is a different issue/noise?

I think we have the same problem. If you take it to the dealer and it gets fixed, please post the resolution. I'll do likewise.

Have had the Same sort of spring / metal sound with my A class (A200 turbo) some years ago. The dealer didnt know what it was, after 4 times at the dealer a MB Tech person from MB Netherlands came to the dealer, after a couple of hours they know what is was. It was the ESP. So you can check your esp light if the sound appears, if it flash it can be your esp . They havent fixed this, because they didnt get an error in star diagnostics :(

My Car is currently at the dealer and they are trying to find a solution for this
 

My car has been at the dealer since Friday and they are trying to reproduce the issue.

so far they have not been able to (of course), even though I told them exactly how to reproduce it like we all talked about in this thread...

if they can't find it, at a bare minimum at least I will have documentation that I took it in for this exact issue before my warranty expired, in case the ***** hits the fan next month and I blow my tranny out afterwards :nix:

i will update you guys if they find anything...

Some more food for thought: I noticed this morning during cold starts, that this spring unloading sound actually happens not from first going into second, but from second going into third (almost exactly at 20mph) if I am not mistaken.

Along with this, the transmission sounds like it partially slips (with a noticeable increase in the exhaust note) and a noticeably "rougher" shift then usual. All other shifts resume as usual.

gosh darn it
 

picking it up tomorrow...

COULD NOT reproduce the noise after trying for 2 mornings in a row they said

I have the same issue as all of you above and it is gonna kill me when my warranty runs out in 10 days and they don't fix it...

what else can I tell them at this point... I guess I have to come in the morning and try to demonstrate with them?

i think you may be right, it has to be second to third gear, as my car is always left in "C" comfort mode which ALWAYS starts the car in 2nd gear and first gear is never used... :crazy:

Well, if I were you, I would call, and tell them not to start the car that morning. Then, when you get there, have a technician or service advisor in the car with you. Describe what they should Listen and look for, and then start the car and drive off. I'm positive that it will happen then.

And yes, that would make sense. I actually drive mine in sport all the time, so it is the second shift. Just from memory I was mistaken into thinking it was the very first. But I verified it the last two mornings.