The car shifts late at high rpm from 1 to 2 with big jerk. I want to check the vacuum system. I think the vacuum goes from brake boost line to vacuum control valve and from there it goes to the 3-way valve and from there it goes to transmission modulator valve.
On top of the injector pump sits vacuum control valve and engine shut off valve. There are several vacuum and vent ports there.
Is there a diagram or picture which shows the vacuum line routing to the white 3-way valve on top of the valve cover? Thanks.

http://www.benzworld.org/forums/attachments/w123-e-ce-d-cd-td/280547d1261437559-vacuum-diagram-confusion-1983-300d-300d-vacuum_shut_off-diagram.gif

First check you have good vacuum going to the brake booster (the main vacuum line).

Check all the vacuum connectors (they rot and split with age).

Check the vacuum line going to the transmission modulator holds vacuum.

If all seems good up top, you can try this:

http://www.benzworld.org/forums/w123-e-ce-d-cd-td/1261744-transmission-flaring-clunking-vcv-diy.html

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

Don't forget about the kick down switch, under the accelerator...if this is bad/not working it will cause hard late shifts.

Also look and see if any of your shifter bushings are bad...

Oh and your car won't start off in first, only if you down shift or use the kick down..

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Thanks for your help guys. I appreciate it. I have read that if you have eliminated the EGR system you can bypass the white 3-way valve on top of the valve cover and throw it away. That would make the vacuum routing a lot simpler. Is this true?

There are few enough people around who know anything about the .118 vacuum-only control transmission setup on these cars. I am genuinely surprised to hear about someone offering advice on hacking the vacuum setup.

Was this advice you read specifically related to this exact model and year?

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

the '80 has the vacuum only trans... normally i'd be the first to suggest eliminating the 3/2 valves but i think you need them for your transmission...

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1981 NA 300D 310k miles

I believe the vacuum control valve is a bleed valve mechanically linked to throttle. At idle the VCV is closed and vacuum is the same as the break boost line. As you push on gas pedal, the VCV starts leaking vacuum and at full throttle vacuum is zero. This is to mimic a gas engine at idle and under load. If all this is true why would we need the white 3-way valve on top of the valve cover?

A properly operating VCV "leaks" at all times.

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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.

Do we need the white 3-way valve on top of the valve cover? That is the question!

Sorry to see this so late. I have owned a 300D for 30 years and they are a little different
than other years because they are a crossover from the 1970's to the 1981 and beyond.

My 1980 300D non turbo had the exact same shifting problem and it was the vacuum
valve on the valve cover the 3/2 valve. After replacing it with parts purchased here
it solved all my problems and I learned how important the little replacement arms are that are also sold here (so you do not have to purchase the entire valve as the arms wear out.
But the valves do leak, and that causes harsh shifting.

So my point is, the 3/2 valve on a 1980 is important for shifting. Do fix it.

On other years, those valve cover mounted 3/2 valves can be removed.

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80 300D 340K Owned 30 yrs
83 300SD 440K Owned 9 yrs - Daily Driver 150mi/day
02 Z71 Suburban 117,000
15 Toyota Prius 2600 miles
00 Harley Sportster 24k
09 Yamaha R6
03 Ninja 250

I had a 1982 240 D in the shop. The car would always stay in low gear and shift way late like the transmission wasn't getting any vacuum.

It had one 3 way valve going for the egr system and one for the vacuum control valve. There was a vac leak in one of the lines connecting the 3 way valves.

Ultimately , the problem was the vcv valve need adjusting. No matter where you put the throttle, there was 20 hg at the trans and at full throttle there would be 6 hg instead of zero. So i adjusted the vcv valve -- there is a little screw under a white cap on the side of it. You can take it off easy and play with it. I turned the screw a little and it made the hg go down to 14 at idle and 3 hg on full throttle. That made the car shift pretty good. She probably needs a new vcv as i couldn't get it to go to zero like it is supposed to do no matter what. But check the vcv.

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

Nice to hear from someone who has owned one of these for that long!

I was also very curious about that 3/2 valve as I know that the 1980 model had only a vacuum shifted transmission no bowden cable/rod, so I personal thought that the 3/2 valve on the models with the vacuum only transmission was important.

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I had very same problem with my 85 SD. It would shift late at 3000-3500 rpm and shift harshly 1st to 2nd. Turned out to be bowden cable adjustment had too much tension on it. Even though the plastic adjuster is broke I was able to adjust it after a couple of attemps. It now shifts at about 1800 rpm and very smooth. Very easy adjustment and did not have to replace broken adjuster as I heard it is a pita job that requires replacement of whole cable into trans and requires dropping trans pan.

The OP's car is a much earlier model of the transmission and doesn't have any Bowden cable or shift linkage attachment to the transmission.

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

I read over and over how important it should be, mine was broken so I replaced it (for $120, they were NLA at that particular time to when I found a shop that had them I bought two) and I never noticed any difference.

So I am happy as well to see a real-world situation where it made a difference. Frankly I always figured I had just done the equivalent of giving my buddy a light with a $100 bill, then tipping him $20....

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22