i HAVE A 1980 300SD THAT I JUST BOUGHT FROM A LYING THIEVING DISHONEST SELLER AND AM TRYING TO WORK MY WAY THROUGH SOME OF ITS PROBLEMS. The transmission was changed out by the previous owner for a used transmission and hasnt right since the change over. Shifts at the right times and down shifts correctly but shifts hard (nearly bangs the drive shaft out) between every shift in a forward gear. No problem with reverse. Any ideas?

Could be either low or over-filled with fluid, measure in ounces if ye add any. Bottom line is normal for cold, top line when warmed up. My w116 1980 300SD also kicked when I'd first got it. When cold could practically burn rubber going from 1st-2nd. It used (or leaked) approx 4-6 oz. tranny fluid in 1,000+ miles at first. Added Lucas trans fluid treatment and has almost entirely stopped.

Heck, it took me coupla weeks just to learn how to drive the car. Soon realized to feather the accelerator anticipating every shift. Must never hammer down on accel pedal when it shifts or will kick like mule! Instaed treat the accel pedal like clutch easing off to control shifts. You'll get to like it after awhile.

If it hammers the forward gear shifts like Thor banging on an anvil, then you likely have no vacuum getting to the transmission vac modulator. I'd check that out and make sure the lines/valve all have vacuum and are connected properly. The hard shifts are classic of no vacuum to the trans.

__________________
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'15 GLK250 Bluetec 118k - mine - (OC-123,800)
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'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
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I'm not an expert, but I second this. Do a thread search for how to measure vacuum to the tranny. There are many helpful threads.

John

__________________
Certified Registered Nurse Anesthetist (CRNA)
2002 F250 powerstroke with Plantdrive WVO conversion
1983 300SD 190K miles ,sold
2006 E320 CDI

you got another YEP on the vacuum line problem. I wouldn't be surprised if a line was not even there....

The vacuum line goes between the tranny modulator (on the driver's side of the tranny) to the tranny valve on the top rear of the fuel injection pump.
Once you get this line connected your tranny will shift a lot cleaner (lets hope) but it will definitely need adjustment since it came off another car. It is currently tuned to the other car's vacuum specs most likely seeing as it sounds like the vacuum isn't even connected.

Good Luck!

__________________
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1974 240d "Peace, Love and Empathy" - Kurt Cobain
1982 300sd "It all depends upon the Benz!" - Me
1983 300sd
1985 500sel
1992 300se

OK guys with your help we have narrowed it down to a bad diaphragm in the vacuum pump...now where can I find one quickly?

The pumps are rebuildable with kits as I'm sure you know. Careful of variations though, MB used 2 or 3 different pump versions. Probly sensitive to VIN# and year. I'd try Phil at the buy parts link on top of this page.

Good news is tranny with recoil like a howitzer does NOT indicate trans on it's way out.

thanks Ill try Phil on Monday

How did you narrow it down to a bad vacuum pump diaphragm. If you have a bad diaphragm, then you have no vacuum and you wouldn't have any power brakes. I'd have thought you'd have mentioned that in the original post because they're a buggar to stop without power brakes.

__________________
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 am going on what my mechanic said...here is his email

"I checked vacuum at modulator and have none, I do have vacuum to the valve at the top of injection pump.
It stopped there. I checked the valve with a mini vac (hand held vacuum pump and the diaphram does not move). It has to have a hole in it. See if you can find this vacuum diaphram because I believe that this is our problem with the shifting."
Anybody help further? car has vacuum and brakes and doors lock.
Thanks to all who are trying to help
Richard

Ok, so it's not a bad vacuum pump diaphragm. He seems to be referring to the vacuum valve that sits on the ip and provides vacuum to the shift modulator.

If it's not working that would explain your problem. Not a real cheap part though if you buy new.

__________________
Joe

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1980 300SD - 495k miles - 'The Ambassador'
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Former Family Members
95 C280
73 280SEL
90 300D
87 300SDL (X2)
86 560SEL
84 300D
80 300SD

Can't really add to the thread but you can do what I did and spend $3000 for a new trans. Now don't you feel better? Hope you get everything worked out.

__________________
Rick & Michele in California
1985 300SD Turbo Deisel
300,000+ miles

1963 Mercury Meteor Stationwagon
1959 Montgomery Ward Silver Pigeon Scooter & matching bicycle
1974 IH Scout 4x4

seems maybe he means the modulator on the tranny end?? did he check the lines to the tranny?

When I bought my car, the tranny hit hard, too. it was not connected to vac.
got it all straightened now,

__________________
1984 123.193 372,xxx miles, room for Seven.

1999 Dodge Durango Cummins 4BTAA 47RE 5k lb 4x4 getting 25+mpgs, room for Seven.

That valve on the IP that sends the vacuum to the modulator isn't currently available from what I've been told. Even from MB USA I was told its on "international backorder", and to check back in a month or two.

Can anyone help me find this part as shown in response #11???
We have identified it as MB# 1230700046. New ones are out of stock with everyone need a good used one quick