Simple as that, will a w123 AT shift without vacuum?

SIL's 85 300D has an intermittent issue where the car apparently will not shift from a gear. The only option is to go to the side of the road, wait, then start up again and it will go.

Im thinking clogged filter or low fluid, but the car seemingly has had some vac issues.

Thoughts?

Thanks!

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Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (113k)
1991 350SD (206k)
1991 300D (228k)
1993 300SD (291k)
1993 300D 2.5T (338k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (265k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)

I have the vac line unplugged from the modulator on my TD.... sure it will shift. It's shifts hard enough to make me yell bad words. One day I will fix the problem.

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08 R320 CDI current

Past
95 E420
87 300D Turbo 5spd
90 300TE
83 300SD
85 300TD
92 400E
85 190D

I'm not sure that is such a good idea. Wouldn't that put extra stress onto the flex discs causing a premature failure?

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-Typos courtesy of my mobile phone.

I agree it's not a good idea. I have a long list of repairs for all my car's. The massive vac problems of the TD is somewhere on that list. Right now the '87 300d on jack stands in my garage for 3 weeks take the top of the list

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08 R320 CDI current

Past
95 E420
87 300D Turbo 5spd
90 300TE
83 300SD
85 300TD
92 400E
85 190D

supossedly hard shifts= longer transmission life. Idk about REALLY hard shifting though

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1981 300SD 512k OM603

My SD doesn't have any vacuum and, yeah, hard shifts. I agree with turbobenz, that will help with transmission longevity and the more stress on the flex discs will be from park, I don't keep my foot on the brake pedal. I figure to replace discs is easier, cheaper too, than to open the transmission.

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83 SD

84 CD

I haven't had vacuum to my transmission for about 6 months since my modulator failed ('81 TD). Yea, it shifts hard, especially the downshifts, but I don't worry about it too much since hard shifts are actually easier on the bands. Of course, it is hard on the drivetrain, but I have learned to put it in neutral for the 3 to 2 and 2 to 1 downshifts until it warms up. Once warmed up, they are just crisp.

I am waiting for the time to replace the modulator and the K1 spring. I'll probably adjust to crisper shifts, since my tranny has 260k and I want to extend its life as long as I can.

Lack of upshifts is not usually a symptom of a vacuum problem. It is typically a symptom of either a stuck bowden cable or a stuck kickdown switch.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13