caliheights

Hi all, my first post since joining the forum. I purchased a used 2009 c300 Pano 6-speed last June 2012. I hadn't driven stick in a decade so I thought it would be fun to get back into it. What I've noticed on this car is that between 1st and 2nd gear it grinds A LOT. That's going from 1st to 2nd and sometime from 3rd to 2nd. The question I have is... how bad is this for the car?? This probably happens 2x per month - which is way too often I have read. Do I just suck at manual? I am seriously thinking about trading it in if this keeps happening as I do not want to destroy this beautiful car! Also, what damage to you estimate has been done so far? Thanks in advance for any guidance or advice!

kevink2

You were lucky to find a manual C300. But, I suspect that 6 speeds are more likely to be driven hard vs the ATX 7 speed.

As long as it shifts properly 90% of the time, and grinds twice a month, it sounds like operator error + a little syncronizer wear.

Going up thru the gears, the 1-2 shift is the most difficult for their syncroniser, vs other shifts, due to the large change in rpm.

A few simple things to try:

I've had cars, like that, and I found that either bliping the gas pedal before the actual lever pull, or a full double clutch eliminates the grind. Finally, if the trans oil has not been changed recently, do it, and consider a specialty gear oil like Redline, Neo, etc, especially if suggested by a member with a manual.

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Glyn M Ruck

I would only use Benz approved oil.

Also make sure that the clutch is disengaging properly.

kevink2

That's good advice Glyn. I mentioned those other 2 because I have track tested them for 1000's of miles with good results in the Rx7 & 924T, and improved cold shifts in the Saab 900 turbo.

Based on experience, I would suggest changing the MB MTX oil every 40K or so, more often if you track the car. Manual trans oil has different properties than plain rear end gear oil, as you know. The "friction additives" for the trans help in smoothly engaging the syncro/gear, and I found that smoothness was rejuvinated with a simple drain and fill.

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Cleanbenz

I have 35000 on my 2010 manual c300 and the shifts are nice and smooth. No grinding unless I'm not paying attention and don't push the clutch in all the way. I'd have it checked just incase.

C300Sport

Mine shifted ok when I bought the car and then turned to total crap after a couple thousand miles. The one/two shift was always the worst.
It had to get ridiculously bad before MB finally agreed to replace the trans. She has been shifting wonderfully ever since.
Make sure your clutch is adjusted properly and shift a bit more deliberately(slowly) especially when cold.
Are you still under warranty? If so, they may be open to replacing the trans as the synchros in some have proven to be less than robust.

Doanster

1->2 is indeed the "problematic" shift. It's just that you have to make sure you are both fully disengaged w/ the clutch as well as fully into second before you re-engage. Other gears/shifts aren't so picky. You'll quickly get used to it and make the mental adjustment. I grinded probably twice early on, but none since.

kevink2

[QUOTE=Doanster;5520193]1->2 is indeed the "problematic" shift. It's just that you have to make sure you are both fully disengaged w/ the clutch as well as fully into second before you re-engage....QUOTE]

That alone will not prevent grinding the gears. With 30-50 K miles on the trans, especially if the shifting habbit put the max load (rpm differential) to the syncros. Wear at the slip/block ring will allow wear at the pre-gear (at the end of the integral main gear. This makes it difficult for the sycro to do it's job, and you will get a grind, with clutch fully depressed, as you are about 1/2 way through the actual shift knob travel.

If you have that crunch frequently:

change out the trans fluid
learn how to truely double clutch when the crunch occurs, just takes practice. Lots of info on web.

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DonjuanOriginal

I have a 2008 c300 6 speed. with 75,000 kilometers on it. It shifts fine. When it's really cold it takes a bit of force to shift into reverse or first. But that's all. The Clutch is more a problem than the gears. audible sound when clutch plate disengages from start up. But like I said it shifts fine. You do have an issue OP. Good Luck


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Glyn M Ruck

The Benz MT is not the greatest & a bit clunky. It needs to be driven slowly & deliberately. It will not tolerate snap changes esp. on the first to second change without protest from the synchros & ultimate synchro cone wear.

The reason I say only use Benz approved oil is that the viscometrics have been optimised for evacuation from the cones & it contains no additives that are aggressive to the cone material composition. A standard sulphur phosphorus axle oil will attack the cones at certain temperatures.

kevink2

My old 924T as well as earlier VW cars required a GL4 gear oil to avoid the high sulphur based additives (found in normal gear oils for high temp shear in GL5 and GL6 spec's) eating away the "yellow" parts. I know Honda was one of the 1st trans oils I knew of that specified their own MTF, or Manual Transmission Fluid, primarily for their NSX as I recall.

The new GM, Mopar, and aftermarket trans oils are blended in a way that they would not pass GL5&6 hypoid bevel gear tests in the rear differential, and as you said, optimised for syncro performance with MTX friction modifiers (not the rear end oil friction modifiers for LSD's)

Sportstick

This has been about the most challenging motor vehicle short of some trucks or a tractor to drive smoothly. Having said that, I still prefer a stick. But in order to up shift smoothly, I find that a quick move of the stick so the clutch can disengage before revs drop too far from the typical 4000rpm shift point is the optimal technique. My trans does not resist on the up shift. Do you think I am speeding up deterioration with this style? I do routinely double clutch for downshifting.

caliheights

THANK YOU ALL SO MUCH for the support! This forum is great. Based on the feedback, looks like its going in the shop next week. Hopefully Smythe (San Jose) can figure out the deal. Oil Change, Trans fluid, and having them check trans and clutch.

caliheights

Also, its was a certified pre-owned car... so I am still under warranty! Whew.

Glyn M Ruck

No ~ as long as you don't feel any resistance to the up change you are fine. If you snap change first to second the transmission will resist the change generally. Especially when cold. You have obviously mastered good clutch control which can be difficult with a Benz MT. While Benz has certainly improved their MT it still lacks the switch like quality of better MT's. Some Benz MT's are better than others from new. The clutch action sucks on all.

Carsy

It is surprising to me that the manual is not user friendly.

I would have thought as the Germans probably use manuals more than elsewhere they would have perfected the shift.

Is there a reason they have'nt ?

Peugeots & VW have.

kevink2

With the Rx7 and it's lightened flywheel, esp in cold weather, I just double clutch in 1->2 to avoid a grind. I just find it's more reliable than timing the engine rpm drop for the shift.

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Doanster

With the demise of manual transmissions in MB cars now, perhaps it was a cost-conscience decision, i.e. why invest in re-tooling/sourcing three years ago when they knew this was the last run?

On a side note, I remember a thread from long ago where it was pointed out that the stick vibrates noticeably more (hands off) while in second gear than any other. Almost like something was just off by a tad and it wasn't fully sync'd or engaged. Any comments on that Glyn/Kevin?

Cleanbenz

After owning several Audi's and VW's I can say that the MB gearbox is definitely more notchy than the others and the clutch pedal is more finicky as well. Not bad all in all but if I stay with MB I'll be going auto anyway. I have no real complaints about their manual setup.

Glyn M Ruck

Most Benz cars sold are auto & they just don't seem to care about their MT's ~ I don't know why they don't buy them in.

As I've said before I think their MT's spoil the cars. I would only buy auto for this reason. That's why I'm pleased they are now offering DCT transmissions for those that want to be more in control.

kevink2

If not fully sync'd you would hear a grind going into the gear. If not fully engaged, sevral bad things would happen, but not lever shaking w/o a lot of noise.

I suspect MB put some noise isolaters in the shift linkage. If so the shaking could be due to a resonance that is based on the typical rpm range in that gear.

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C300Sport

I would agree with this for models like the E, S, GLK, ML etc but think that the C, SLK, E coupe and even the SL would be nice with a manual trans...of course improving the manual is sorely needed, especially if it were to be offered in an SL.
I do believe the SLK250 is the soul manual hold out in the US line up. Has anyone driven one of those?

caliheights

$687 for B service at the dealership! San Jose CA. Rip off?

Bosnia1992

that's the biggest rip off, mine was 258 , I just had them do the oil change and that was already pre paid because I purchased a lifetime oil change program and I did the rest , you're in California there's more than one dealership there , I'm stuck with one Mercedes dealership in the whole state .


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