I found one of these in my top tool box tray after I kicked it over in he driveway behind my car. I had been asking at all the auto stores for one of these and was going to try the dealer next . Needless to say, finding it renewed my faith after picking up about a hundred screws, bolts, and nails accumulated over the last few years. .

The piece i am talking about is a tiny vacuum coupler (2 male ends) called an "orifice" that you join 2 vacuum lines/Ts/etc with. The key feature is that one hole is smaller (needle point size) than the other so it reduces the volume of vacuum out the small pin hole end . That this piece is important has been mentioned several places but I never knew exactly what its effects were. Except I did read turning it the wrong way ruined the tranny on someones car and I am still curious about that. I went to an Indy and tried to get an orifice. The diesel mechanic did not know what I was talking of and was quite sure the only thing that affected vacuum at the tranny was the VCV and it had an adjustment screw. Lucky I never trust anyone except people on the internet .

Nuf Rambling fool. ! Ok,, here is what the black orifice I found in my tool box tray did for my 1981 300D. I named it "Blacky" And mind you this orifice may not even be the right size (a tad small if anything) as they come in many sizes. I can post a color coded chart from service manual if someone wants. First, my problem (posted several places ) was flaring in all shifts when I had *any* foot on the pedal whatsoever -- a real pain when you pull out into traffic. Also , the kickdown switch did not work at all but I had dismissed this as a separate issue. I got the car with these problem and varuum lines wired all wrong and crossed. Someone put a new engine in and never got the vacuum right. I guess they did not have internet access. One was put on the metal dashpot thingy on Injection Pump that looks like it wants something hooked up to it (but does not i figure) instead of the vent on the VCV valve. Swithching that made the car much more peppy.

So, first was to fix vacuum wiring and eliminate any excess variables by following the diagram and ditching the black box 3/2 valve and tightening up vacuum leaks. I did this and this made flares a little better (could give it a bit more foot ) but still it flared under most conditions.

Enter Blacky the vacuum orifice between the vacuum source and green VCV dashpot T (one end to VCV, one end to tranny). Great scott, Blacky is like Tranny's brain and now the car can run like the Black Stallion.. When I put my foot on it, not only does Tranny not flare , it stays down a little while longer giving extra acceleration. Like it knows I want to go faster It accelarated up a big hill to 30 mph that it usually decelerates up because it stayed down in 2nd gear. No one told me it was supposed to do this. I have not had an automatic in about 3 years. Amazing how It shifts much more consistent with how I would if I were doing it . Also, if I am in no hurry and taking it easy, IT shifts earlier keeping my ride smooth as can be and mpg as good as can be -- into 3rd at about 17 or 20 and 4th at 27 - 30 like it used to but with no flare.

And the kickdown switch works now! It was bone dead before. And I think my climate control temp dial is more responsive.

Other stuff may work better too. I bet if this fixes my cold starting problem and grinding starter

Hope all your car days go smooth.

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What Would Rudolph Do?
1975 300D, 1975 240D, 1985 300SD, 1997 300D, 2005 E320 , 2006 Toyota Prius

Don't you just love it when things like this work?! Excellent. Congratulations.

Of course, if you're like me, the next thing you'll find is a screw (from the kicked over tool box) in one of your tires. I came up one screw short (on the car, not me) when putting the splash pan back under the 190D last week. Next day I find the Eurovan with a flat in the driveway...yepper, must've kicked that screw out into the driveway so it could get planted right smack in the center of that tire (captive washer held pointed it up at just the right angle). At least I found the sucker, and now it's back in the Benz.... !

Many folks don't realize the importance of that small orifice to allow the VCV to do the proper modulation for the transmission.

With just a vacuum gauge and a bit of patience, many of the problems caused by excessive flaring or hard shifts can be eliminated.

Your success proves that a checkup of the system and carefully returning it to specification will provide significantly improved driveability.

Everyone with shifting problems should note this success and take heed.

I was "apprenticed" for one day by the top guy of Mercedes transmissions on the West Coast. I recall he said that there are at least 4 types of these little controlled vacuum splices thingies, black, yellow, tan or brown and green. Either the tan or green one is a solution for early shifts. Adjusting the controlled leak at the rear of the IP is also key to setting up a transmission to shift where it should. He said he was certain that more than a few shops told customers they needed a transmission rebuild when all they needed was to set up the vacuum systems properly.
The first thing he does in checking a transmission problem is drill out the manifold connection, the one that has a small opening (one has a large hole the other a small one). If any dust accumulates in that then the source vacuum deteriorates and all efforts are in vain.
Then he blows air thru this Blackie splice (or green or tan whichever is on the car) to clear it open, then he plugs the lines going to the CLS to remove it from possible interaction (leaking CLS can affect vacuum overall) then he tees in a vacuum gauge to the transmission line. The rest is experience, how far the vacuum needle swings when the accelerator is advanced and let go is what you want to look for. I still have the marks on my vacuum gauge where he specified.
If that doesn't work then you attach hydraulic pressure gauges to the transmission and start taking readings or bench test it.

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

I have a 300D and I'm trying to get a hold of one of these, but I'm not sure which ones I'm looking for. You say this is different from the green dashpot? My diagram says I need 2 orifices 1 by the booster line and 1 by the T from the 3/2 valve.

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1980 300D 300K KM - parting out
1979 300D 375K KM - parting out
2 300Ds for sale

They look like just a little vacuum hose connector. You will only see a little strip of plastic between the two hoses.