Ive been having trouble with my 1980 300d auto transmission shifting properly. I was told by many that it could be a vacuum issue but my mechanic said it was more than likely the transmission. I had trouble beliving him since he didnt even check the vacuum lines. Originally it would shift propely if I steped on the accelerator nice and gentle. If i didnt do that, it would not shift and once past 20 mph I would have release the accelerator and that would kick it into 2nd. Once in 2nd i would have to to the same thing to shift to 3rd but it wasn't as noticable. After changing the vacuum lever on the 3/2 vacuum valve(was instructed it would help) I noticed that it doesnt shift with a gentle touch anymore, it only shifts by releasing the accelerator after it flares past 20mph. Im hoping its not the transmission since mine is vacuum modulated and the only ones I could find are mechanical modulated(frankly I have no idea if there is a difference or if it would fit mine). I will have the vacuum lines/modulator and vcv checked soon and if im told its truely is the transmission I would like to be positive before I rebuild or replace. Any info would be helpful

Thank you

Johnny,

Do check you vacuum lines. Check your bowden cable at the(check to see if it did not disconnected it self) throttle-Screw it in to shorten the shifts. The travel adjustment is about an inch. The modulator on the outside of the transmission has a knob or key with a 30degree travel adjustment.

Also, you should have at lease 2year old fluid and filter. The fluid should be upto level too.

Try those,

Martin

MAVA,

Excuse my ignorace, but I haven't had much time with the car and I was told my year model didnt have a bowden cable. My experience with w123's is limited.

The vacuum modulator fastens on the outside of the gearbox, I think and they aren't hugely expensive.
Do your brakes have the same level of vacuum assistance as before the shifting problem?

If you post this thread in the diesel discussion forum, you may have better luck. The people there are experts on the diesels and can probably answer your questions.

The 1980 trans is 100% vacuum controlled. If you disconnect the vacuum line to the modulator, the trans should shift at MAX RPM and hard!

If that is the case?? then the trans is OK, and the vacuum controls are the problem.

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+1 on the above. You have a vacuum leak somewhere...

My transmission shifts this exact way...at the max rpm, unless I let off the accelerator....mine is mechanically controlled with out vacuum....I consider it normal....

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The little 3/2 valves be the source of a Vacuum Leak and that can effect shifting.

You might trace from the Main Vacuum Line and find where it branches off to the 3/2 Valve or Valves and disconnect that line and Plug off the Vacuum Side and see what happens.

You did not mention if you are having issues with the Locking System or not shutting down normally?

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84 300D, 82 Volvo 244Gl Diesel

The locks and shut of are actually very good. never had an issue with them so far? I this a good thing for my situation?

IDK, I seem to remember a bowden cable on my wagon... it was a 79... although I also drove an 83... I could be mistaken.

do you have a picture of your throttle linkage?

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My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
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Here is a picture of my 3/2 valve I just noticed that II port is capped of and removed the line from 1 and drove it....Wouldn't shift at all. Placing it back made it shift again and almost made it shift a bit smoother yet didn't fix the problem. And here is a pic of the throttle linkage

Just based on the color .. or lack thereof... of your vacuum lines, my money is on your vacuum system. Someone has either been playing with your vacuum system or the MB has sat with the hood up for many summers.

Follow the prior suggestions for diagnosing and lets see where we are.

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Umm your missing the line that runs to the transmission. The only thing hooked up to the 3/2 valve is your egr system here is the vacuum diagram. Find out where the line is that runs from the transmission and plug it in to the port that is capped...

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