Hi,
I am new to this forum. I will be purchasing a 1985 300D Turbo Diesel that has 185,000 miles, and is in pristine condition, inside and out. It starts right up cold, and runs smoke free once its warmed up. However, it shifts extremely hard into second gear. All other shifts are like butter. I am hoping that this is a vacuum, or modulator problem, and not a tranny problem. The previous owner says that it has always been like this since he has owned it (9 years). I tried searching the forum for a process to go through, but could not find one. If someone can lead me in the right direction I would be grateful.
Jonathan

Does it shift that hard when cold only, or all the time? Mine shifts hard when cold, but when it's warm, it's better.

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It shouldn't be REAL hard from 1-2, but a jolt/generally hard shift is normal for the 1-2 shifts....and the rest of them should be firm but smooth, you should feel them engaging. MB designed them this way and it reduces interior clutch pack wear, making the tranny last a loong, looong time.. (200k+ easily)

I like the hard shifts, but thats me, I want to know when it enters each gear.... Modern cars with their slippery transmissions that you can't feel weird me out.

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I would suspect a vacuum problem. A quick and easy test would be to disconnect the vacuum from the modulator and see if there is any difference with a test drive. Replacing all of the flex fittings, for about $12, cleared up a lot of shifting problems for me and eliminated them as a possibility for leaking.

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Sam

84 300SD 350K+ miles ( Blue Belle )

I've found that leaving your foot on the floor smooths out the shift

In all honesty though...an ALDA adjustment and whatnot will most likely up the power a bit and smooth out that shift.

Thats what I did on my 300SD and the 1-2 became much more resonable.

There is so very rarely a problem with the 1-2 actually having serious issues (other than adjustments) that I wouldn't worry about it too heavily when considering the purchase of the car.

How is it otherwise?

You said what I wanted to say better than I did. That's what I meant.

I've seen a couple that would break the back tires loose on the 1-2 shift.

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Jim

That little black key on the dash that turns,its a choke ,turns your idle up when its cold out or down after engines warmed up .Counter clockwise is idle up I believe, this I noticed will make a hard shift from 1st to 2nd if idle is turned all the way up.Turn down the idle and your shifts should be smoother.

His 300D does not have the idle adjustment knob (it's not a choke).

A properly adjusted transmission has firm shifts, but they should not be "extremely hard" as you've described. Try adjusting the modulator to soften the shifts up a little. It's possible that the modulator has been set firm to compensate for too soft shifting or flaring in other gears. You may want to get this looked at prior to buying the car.

Hey, welcome to the forum.

I have a brother in Port Orchard, he's on the police dept. there.

The first thing you need to do to troubleshoot transmission shifting is to check the vacuum system. There are lot's of tutorials on how to do this. The tool you will need is a mity-vac.

http://www.continentalimports.com/ser_ic20242.html

http://www.mercedesdismantlers.com/722.3and722.416_transmission_adjustments#722.3%20Series%20and%20722.416%20Transmission%20Adjustments

http://users.vnet.net/w123d/w123d/transmission.htm

Danny

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1984 300SD Turbo Diesel 150,000 miles

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Thanks,
I appreciate the links.
Jonathan

I didn't realize that I reply to all posts at once!
I'm kinda green at this, so what's an ALDA adjustment?
When I say it shifts hard, I mean that if you are trying to accelerate it snaps your head back!
Other than the shift issue, the car is a beauty. One little dent on a rear fender the size of a paper match stick. The engine is clean, and runs clean and smooth once warmed up. Interior is perfect, no tears or even looseness in the upholstery. The trunk looks like it was never used. It does need a vacuum acumilator though, as the original needed repair, and the owner bypassed it. I think the only thing affected is the door locks, maybe a trunk latch mechanism (if the 85s had that, and possibly the air heating air duct flap). I'll probably look for a new acumilator and put it back to spec..
Steering is tight, suspension is soft but not too so, no clunks. For $2,500 seems like a great deal. A lot better than the $11,000 I spent on my 1992 300SD that now confuses lube oil consumption with diesel consumption. It goes through a couple of quarts per tank as I smoke out the neighborhood!
Thanks to everyone for the help.
Jonathan

This is usually a vacuum transmission modulator issue.

As someone mentioned above, the quickest confirmation test is to disconnect the vacuum line that runs to the transmission modulator. It should be in the vicinity of the oil filter cannister and run down towards the driver's side of the transmission. If there is no change in shifting when you disconnect it, you're not getting a vacuum modulation signal to the transmission. If you confirm that's the case, come back and tell us and we'll concentrate on that problem.

My particular episode with this was due to an incorrect hookup configuration on all the vacuum works on that side of the engine. Someone probably knocked it loose during an oil filter change and valve adjustment session and hooked it all back up wrong.

The consequence to letting the transmission shift this way over long periods of time is severe differential wear, possibly to the point of failure. So, at some point you need to check how loose your differential has become. If you get a clunking from the drivetrain in transition from acceleration to deceleration, the differential may be worn.

Ken300D

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1982 300D at 351K miles
1984 300SD at 217K miles
1987 300D at 370K miles

Doggone it. Anyone have a spare differential for sale? How much do them jokers go for?

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BTW the diffs can be shimmed and adjusted...its tricky and not so much a DIY job but if you have the means and its affordable, it can be repaired back to spec.