The car runs very well and hasn't had any trans problems since owned by me. The fluid and filter are relatively fresh (last year) and the fluid appears clean and smells fine.
I have defeated the EGR valve and associated switching on the valve cover. I have also adjusted the VCV for full travel and since doing these things it has shifted flawlessly.
It has no Bowden cable, only the vacuum line and a wire (2 total) running to each side of the trans from the underside of the body.
Today it suddenly began upshifting very early regardless of pedal position and was winding up in 4th at 25mph. When I attempted to hold it in gear with full pedal it shifted back and forth from 4th to 3rd rapidly and repeatedly. I removed the VCV and it seems to be working fine-holding vacuum when closed and bleeding it off when open.
I took a drive with the vacuum totally disconnected from the trans and it made no difference in the shifting behavior (this may be the most telling of all symptoms from the searching I've done). Oddly, the car doesn't downshift when slowing down even with WOT at very low speeds.
It shifts fine when rowing through the gears "manually" with no apparent slippage or flaring. Also, now it doesn't "hunt" from 3-4-3-4 like it did earlier-it merely stays in the higher gear.
The electric kickdown switch seems to have no effect on the situation.
Open for suggestions. I will have intermittent computer access until Sunday night (8/1) so please don't be offended if I don't post until then.
Thank you in advance.
Chuck.

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1983 M-B 240D-Gone too.
1976 M-B 300D-Departed.

"Good" is the worst enemy of "Great".

You have a control pressure rod somewhere, they're were different set ups, so I can't say for sure where. See if there is an adjustment on it.

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83 SD

84 CD

Is that the telescoping rod in the throttle linkage across the top of the valve cover. I'll check into that.
Wouldn't removing the vacuum from the modulator altogether cause harsh late shifts though. Mine didn't change when I did this.
Thanks!

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1983 M-B 240D-Gone too.
1976 M-B 300D-Departed.

"Good" is the worst enemy of "Great".

One of those rods, don't know which one. Is there one seemingly coming from the firewall direction? See pic.
And I would think you'd have hard shifts without vacuum, I do.

Attached Thumbnails

 

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83 SD

84 CD

Make sure all of your linkage rods are tight and secure...I had a similar problem with my 240D, and as it turns out, the linkage rod to the trans just needed to be tightened.

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Current cars:
2000 ML55 AMG, 174k miles
2003 C240 T-Modell, 202k miles
1995 S320, 207k Miles

There is no mechanical linkage to the trans. Only a vacuum line and the two wires mentioned previously.
What could cause the trans to be seemingly unaffected by the disconnection of the vacuum line?
Thank you for the replies.
I'm back from the family reunion and will check the control rods and linkages tomorrow evening.

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1983 M-B 240D-Gone too.
1976 M-B 300D-Departed.

"Good" is the worst enemy of "Great".

If there is no change with the vac line disconnected, then I would say it's safe to assume that the trans is either getting no vacuum (or not enough) or the modulator is bad...

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Current cars:
2000 ML55 AMG, 174k miles
2003 C240 T-Modell, 202k miles
1995 S320, 207k Miles

That's kind what I was hoping for. I know with a good modulator, absence of vacuum will cause late hard shifts but with a bad modulator it can behave as I've described?
Any one else vote on the modulator? Other thoughts?
Thanks!

__________________
1983 M-B 240D-Gone too.
1976 M-B 300D-Departed.

"Good" is the worst enemy of "Great".