Last Wednesday I noticed every upshift was holding longer than normal and flaring. It came on very suddenly; I left the house and it was shifting fine, 12 mile jaunt down the freeway constantly in 4th, and then the final leg to work (2 lights and a stop sign) my transmission started flaring. 1-2, 2-3, 3-4. Now, no change hot or cold.

Once it has shifted, it doesn't slip abnormally. Up til now it has shifted kind of hard due to (I believe) a vac leak at the modulator. I've adjusted the VCV with only very minor improvement.

What do these symptoms point to? B2? Some adjustment needed? Could the supposed vac leak have fixed itself (thus the CV is now over adjusted)? Any help is greatly appreciated.

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1984 300TD Turbodiesel - 272k
- Daily Duty
1985 300D Turbodiesel - 315k
- "Recommended for competition events only"

you shouldn't adjust the vacuum modulator on the transmission until everything else is worked out....the list of things a transmission should see when issues arrise is...

fluid/filter change with dex/merc fluid

check the dip stick when the car is at operating temp and idling in park, should be between the two notches

confirm shifter bushings are good

confirm kick down switch behind accelerator works

confirm firewall pivot mount is good

verify/adjust all linkages to fsm spec

check/adjust bowden cable

Confirm/tune engine...new filter air/fuel, no air leaks in fuel, valve adjustment, injectors, alda...

once this list is gone through, then you can start looking into the transmission itself. A transmission will only work correctly if everything else is working correctly to tell the transmission when to and when not to engage..

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maybe you had a failing check valve at the pump and before it wasnt producing enough vac and the broken pieces have moved position to where its now pulling more vac?

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1981 NA 300D 310k miles

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I dont believe that vac is over adjusted as you say...it is easy to test it
plunge the vac line to the tranny (from vcv) and see if slippage is still there.
you will have some bangs through gears ...

.

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w126 500SEC gen II euro, powered by OM617 turbo stolen from 84 300SD 2.88 diff,EGR blinded
next wish/project: w114 coupe OM603 powered

One thing you may want to check is that the white plastic clip piece that joins the short section of throttle linkage that operates the VCV is still in place and the linkage is moving the VCV's arm up and down.

These get brittle and break. When that happens the VCV is no longer bleeding off vacuum and your transmission behaves badly.

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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

Maybe some valve is gummed up.

Treat with a trans-fix solvent and afterward change fluid and filter?

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1979 300D 220 K miles
1995 C280 109 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles SOLD
********************
1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD