Greetings,
I have a 300D that has sort of soft shifts. They're not super soft, or really sloppy (although it slips sometimes going from 2nd to 3rd when I don't accelerate hard) but I'd like them to be just a bit harder. Is there a way to do this? Do I have to alter the vacuum going to the transmission? By the way, I do have a very slight vacuum leak somewhere as the locks don't work in very cold weather. I suspect when it's cold out, the vacuum lines harden and the leak gets a little worse. When it's atleast 35 or 40 degrees out, the locks work fine and seem to hold vacuum overnight. Thanks a lot for the info. I think slightly harder shifts would give me a bit more confidence when I drive this otherwise marvelous car.

Alex

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1983 300D (parked for four years)
2012 VW Sportwagen TDI Manual
2001 Miata SE
1962 Chevrolet Corvair Rampside

Most of us are trying to keep our transmissions tuned up so that they shift smooth. Maybe you are luckier than you realize...

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1982 300D Turbo "Helga"
380,000 miles

Not having a Diesel Auto at the time, I can't remember the details but I believe that there is a piece on the side of the transmission that you can pull out and turn a few clicks to control shift firmness.

Hope this helps. Hopefully someone more knowledgeable will give greater detail.

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2008 GL320CDI 6K
1970 280SL 112K
1982 240D 210K (Sold)
1973 220D 220K (Sold)
1967 200D 160K (Sold)
1992 400E 139K (Sold)
1988 300E 148K (Sold)
1987 300D 257K (Sold)
1991 300E 108K (Sold)
1987 300E 131K (Sold)
1978 300D TMU (Sold)
1980 300D TMU (Sold)
MBCA Member

The vacuum modulator is on the left side of the transmission, it's the part that the vacuum line attaches to from the engine. You can try making a minor correction to the setting. Just remove the rubber cap (making sure it's in good condition). There is a sheetmetal "key" under the cap. Pull the key out halfway so the head of the key can be rotated. To make the shifts harder, you would turn it counterclockwise, I would do only 1/4 turn at a time, be sure to reinstall the cap before testdriving it.

This is for minor changes only, severely hard shifts or extremely soft or slipping upshifts indicate probable malfunctions elsewhere in the system, which should be attended to before a internal transmission failure can occur. Also if there is ATF in the vacuum line at the modulator would mean you need a new modulator as the diaphragm has failed.
Gilly

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Click here to see the items I have up for auction at EBay

Click here to see a photo album of my '62 Sprite Project Moneypit (Now Sold)

My 240 had a soft shift like you described.
First I change the fluid and drained the torque converter. Then adjusted the modulator. It may be gummy or dirty fluid. Any way it cured the problem. I agree soft shifts feel like something is wrong.

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Ricali

03 C240 4matic wagon
95 300E 234,000
7 prior 240;s 5 still going
81 300sd gone
65 230sl gone
49 Studebaker Champion
90BMW convert.167,000
60 Dodge D-100

Thanks for the info on the transmission modulator. Is it easy to access from under the car? I'll take a look tomorrow and see what's up.

Brad:
You may end up being right about being lucky.

Alex

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1983 300D (parked for four years)
2012 VW Sportwagen TDI Manual
2001 Miata SE
1962 Chevrolet Corvair Rampside

Alex:
Just one correction, for harder shifts you need to dial it clockwise, not counterclockwise. Just like a faucet. When you turn most faucet handles clockwise it shuts off, counterclockwise it opens up more. You want less vacuum, not more, so turn it clockwise. You have to realize that the control system on the transmission isn't much different than a gas engine. The plumbing and valves on the Diesel are set up to imitate what the vacuum on a gas engine is doing. Hard acceleration=less vacuum on a gas engine=later and harder shifts. Less acceleration =More vacuum in a gas engine=earlier softer shifts. The vacuum modulator in general controls how hard or soft the shift is, the throttle cable works much like it does on a gas engine and contols how early or late the transmission shifts.
You may be able to do it on the ground, never had to try it.
Gilly

__________________
Click here to see the items I have up for auction at EBay

Click here to see a photo album of my '62 Sprite Project Moneypit (Now Sold)

Did you look at the Tech section posts? there is a complete description and picture for what your looking for

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Ricali

03 C240 4matic wagon
95 300E 234,000
7 prior 240;s 5 still going
81 300sd gone
65 230sl gone
49 Studebaker Champion
90BMW convert.167,000
60 Dodge D-100

Some people like a personal response to their question, that's what I'm here for, that's why I get the big bucks.
Gilly

__________________
Click here to see the items I have up for auction at EBay

Click here to see a photo album of my '62 Sprite Project Moneypit (Now Sold)

Dan,
Thanks for the great explanation of what to do and why it's effective. I'll have a look when I'm changing my oil tomorrow.

Ricali,
Thanks for the tip on the Tech section. I'll do a search for transmission info in the archieves.

Alex

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1983 300D (parked for four years)
2012 VW Sportwagen TDI Manual
2001 Miata SE
1962 Chevrolet Corvair Rampside

Gilly, Alex

The vaccuum modulator on my 81 300D and 80 240D is on the right side of the transmission as viewed from the drivers seat. It is red on these years. There is no rubber cap on either of mine, but is a white hard plastic cap, held on by a interior pinch clip.
Squeeze the clip and pop off the plastic cap with a screw driver.
Underneath this you will find a sheet metal "T" key thingy. Pull this out a little(you can pull it out all the way and it will fall into your hand) and you can turn the valve inside. There are slots on the red housing where the key locks into. Use these slots as references for adjustments, and put the "key" back in and put the cap back on to test drive. Hook up the vaccuum line too .

Please note that if you cannot hold vaccuum on this modulator, it is easily and cheaply repaired by simply replacing the O-ring under the white plastic cap! Cool, huh?

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Ed
1981 300CD (Benzina)
1968 250 S (Gina) 266,000 miles!
1983 Alfa Romeo GTV6 (Guido)
1976 Jaguar XJS-saved a V-12 from the chevy curse, what a great engine!
1988 Cadillac Eldorado (better car than you might think!)
1988 Yamaha Venture (better than a Wing!)
1977 Suzuki GS750B
1976 Yamaha XS 650 (sold)
1991 Suzuki GSX1100G (Shafty Gixser)
1981 Yamaha VX920RH (Euro "Virago")
Solex Moped
1975 Dodge P/U camper


"Time spent in the company of a cat, a beer, and this forum, is not time wasted!"

Alex,

CHECK OUT THIS LINK!!!

http://www.mercedesdismantlers.com/722.118_transmission_adjustments.html

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Ed
1981 300CD (Benzina)
1968 250 S (Gina) 266,000 miles!
1983 Alfa Romeo GTV6 (Guido)
1976 Jaguar XJS-saved a V-12 from the chevy curse, what a great engine!
1988 Cadillac Eldorado (better car than you might think!)
1988 Yamaha Venture (better than a Wing!)
1977 Suzuki GS750B
1976 Yamaha XS 650 (sold)
1991 Suzuki GSX1100G (Shafty Gixser)
1981 Yamaha VX920RH (Euro "Virago")
Solex Moped
1975 Dodge P/U camper


"Time spent in the company of a cat, a beer, and this forum, is not time wasted!"

Ed,
Thanks for the info and the fantastic website. The picture really helps me visualize what I have to do. Just to reiterate, the modulator is on the passenger side of the transmission under the car. Correct? If it is, no need to respond. Thank you.

Alex

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1983 300D (parked for four years)
2012 VW Sportwagen TDI Manual
2001 Miata SE
1962 Chevrolet Corvair Rampside

Since getting the 240D up and running and seeing how one of these transmissions are supposed to work (thanks gilly!) I spent a little time on the 300D tranny this afternoon. The 240D tranny works GREAT - drops done when I put my foot in it and lets the engine come on up in rpm like it is supposed to. As a matter of fact, the 240D seems like a sports car compared to the 300D. Anyway, I installed a new vacuum controller (round blue thing on the drivers fender well) and turn the "tee" on the modulator in one full turn. Does not seem to be any change except for what seems to be a little slippage when going into high gear. The last time I tried the new vacuum controller I did not adj the modulator and got severe slippage. I will try to get a vacuum line diagram and make sure I have everything connected properly. The car has always shifted into high gear by the time I get to 30 mph so until I got the 240D going I did not really know what it was supposed to feel like.

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Jim