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Almost every time I switch into the second gear, a quite loud crackle sound is heard shortly. It only happens when switching into the second gear, other gears are fine. I depress the clutch fully of course.

The vehicle is a Mercedes-Benz 308D, a T1 van, year 1992, model 602.316

The transmission is a 5-gear manual gearbox - type G1/18-5/4,69 (some sources describe it as G1/18-5/4.7) model 711.113.

Is it something to worry a lot about?

How to fix it?

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I think this could be related to one if the gearbox synchronizers (take a look into this wikipedia article) to see what I mean, and the one that's failing is the one for first-second shifts, as you describe the issue.

I hope that helps

  • might want to ask about the third to second downshifts as well. – Bob Cross Apr 17 '11 at 14:20
  • I think if they're not producing noise at this time they could still be working, remember using the truck on a city would result using 1st and 2nd gears all the time, so these will wear the most. – Eugenio Miró Apr 17 '11 at 14:50
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I agree with Eugeio in that it sounds like a synchro. Have you changed the rpm point that your shift or hauling a heaver load recently then usual? In my truck if i shift around 2500-3000 RPMs with a decent load behind it the gears will grind a little bit. So if i shift before that point then i dont hear anything.

  • This noise switching into second gear is there since ever I bought the van last year. I can't really tell is it related to at which RPM is the switch, as the van doesn't have a tachometer (I'm planning to retrofit one). – miernik Apr 17 '11 at 23:02
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My car+tranny has (and is KNOWN for) this issue.
If I shift into 2nd from 1, it makes a clunky noise. When the engine/fluids are still cold it will do this EVERY time and is quite loud.
If I shift from 1 => N => 2, then the noise does not appear.
Shifting from 2 => 3 rarely does it and 3 => 4 even more rare.
Once completely warmed up, it rarely does it, period.

In my case, the cause are the synchros.
The known mitigation is to use some "special" transmission fluid.

I have not changed out my fluid to the special fluid so it keeps making the noise, but it isn't really anything to be worried about unless you are having a hard time putting it into gear. If you are having a hard time putting it into gear, then those synchros are probably messed up and will only get worse and worse, and it would already be too late to do anything about it.
If you are worried it's killing your synchros, you can try to do a fluid change and have a oil analysis done to check for synchro material in your fluid.
You can try double-clutching and see if that helps with the noise.

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