Hi all,

Long time reader/appreciator of this forum, first time poster. I hope the transmission experts can offer some advice on this situation:

Last week I took a long trip (1,300 miles over 3 days) in my 1982 300D and the car performed perfectly. I returned home and didn’t drive the car again for four days. Now the transmission violently slams into gear when it shifts. The shift points all seem to be the same as before, and the slamming happens during both upshifts and downshifts. Trans fluid level is normal. Could this be a vacuum adjustment problem that suddenly occurred, or does this sounds more like a component failure?

The transmission had a small amount of flare on the 1-2 shift previously, but it was completely tolerable. I can’t drive the car the way it’s shifting now without risk of neck injury!

Thanks,

Charlie

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05 E320 CDI - 175K miles
82 300D - 200K miles (sold)

Sounds like a vacuum problem to me. Check the vacuum levels with a Mity Vac but it sounds to me more like a broken fitting or disconnected line.

__________________
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

I agree. I disconnected my vacuum line to the transmission once (just to see how it would shift) and it was pretty rough.

__________________
John Schroader
bio burnin' 83 300D, '83 300 SD, '79 240D
"I've never met a man who was good at making excuses who was good at anything else" Ben Franklin
"You cannot permanently help a man by doing for him what he could and should do for himself" Abraham Lincoln

It sounds to me like a vac line came loose or broke. Usually leaks to manifest themselves that way. Leaks usually start out slow and get worse and worse causing the transmission to shift harder and harder. I would poke around the engine compartment and look for a loose vac line. Does everything else work okay, ie door locks, breaks, engine shut off?

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Yes, all the other vac-related systems work just fine, but I'll check around this evening and see if I can locate a loose or damaged vac line or connector.

Thanks for all the quick replies!

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05 E320 CDI - 175K miles
82 300D - 200K miles (sold)

On the way home from work today, I felt a harsh downshift from 3 to 2. I thought , "Uh oh, vacuum problems." Sure enough it also shifted hard from 2 to 1. I pulled into Barnes and Noble and the engine took forever to shut off. I looked under the hood for a problem. Couldn't find any. Bought a book, then continued my drive home. No further problems.
Stuck check valve? Intermittent leak? Bad ignition switch? It happened once before, about a year ago and went away. Not going to worry about it until it continues to happen.

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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

Spent some time this weekend hunting for a loose or broken vac line. Came up with one that was completely disconnected at one end. Unfortunately, the disconnected end is behind the firewall, so I have no idea where it’s supposed to connect. Anyone know what this line goes to? (Please see red arrow in the attached photo).

Also, am I risking any damage to the car by continuing to drive with such harsh shifting?

Thanks!

Charlie

Attached Thumbnails

 

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05 E320 CDI - 175K miles
82 300D - 200K miles (sold)

Picture's too small for me to get a good look. There is supposed to be one open line inside the car. It's a vent.
Did you check the connections at the transmission?
Put a Mity Vac on the lines to see what kind of vacuum you are getting.

__________________
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

That is a vent line. It is supposed to be loose on that end. It allows clean air to be sucked in for the vacuum control valve, so you'll have to dig a little deeper.

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Great, thanks, Andrew. I'm ashamed to admit that I don't have a MityVac (yet); I'll have to get one, Kerry, and keep working...

Thanks again, gentlemen.

Charlie

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05 E320 CDI - 175K miles
82 300D - 200K miles (sold)

Turns out it was a cracked vac line going to the transmission modulator. Had my local (and really great) indy shop diagnose and repair. They also adjusted the modulator and it shifts better than ever. Best hour’s worth of labor I’ve spent on the car yet.

Thanks for all the helpful input!

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05 E320 CDI - 175K miles
82 300D - 200K miles (sold)

Glad it's fixed, but get on the Harbor Freight website and order a MityVac. It costs about a third of an hour's labor. The satisfaction of diagnosis and repair can then be yours.
I was rereading Exodus in Hebrew the other day and was surprised to discover that "Honor they Father and Mother" has an alternative translation, not typically found in most English versions "If thee buyeth an 80's Mercedes, thee must also buyeth a Mity Vac. Do so and thy days will be long upon the earth and thy car will continue to suck properly. Thus saith the Lord "

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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

Well put, Kerry. Can't argue with the "good word."

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05 E320 CDI - 175K miles
82 300D - 200K miles (sold)