Hey all, I'm a newbie to this forum and Mercedes diesels in general, so bear with me if all this is a repeat!
Just got a 1981 300D and it runs great, but seems to shift late, especially into 4th. I have seen other posts here referring to a bowden cable, and suspect this may be an issue here, since the trans was supposed to have been "rebuilt" recently. My Haynes manual is not very specific in this matter, and I am counting on the good will of all you good folks to help me resolve this.
I am mechanically inclined, and, given the right info, should be able to carry out the needed tasks.
Thanks in advance!

this may differ on your model, but this is how it is on my 83 300SD(same engine i think). The bowden cable is attached dirctly to your trottle linkage, it should be one of the only cables,with a blue(or white i don't remember) rubberish plastic bolt that can be turned out or in. I beleive to soften the shifting, you want to turn this cable out. Try a little bit at a time, if you mess with it too much your car will start out in 3rd(NOT good) hope this helps
R

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83 300SD.......sold
96 integra SE....sold
99 a4 quattro....sold
2001 IS300.......sold
2002 330i.........current.
2004 highlander limited....current.

Thanks for your reply. That don't seem to be it, I messed with it a little at a time each way, no luck. What the car does, is revs really sorta high before shifting, in all the gears. Not like its gonna blow up, but higher than normal, compared with my 83 300D turbo.
It doesnt shift really hard or really soft, just waits too long to do it.
I notice after it has warmed up a while, it does improve some, so I checked the fluid level and it seems to be in the 'Middle' of the marks when warmed up.
Big problem is, it's the wife's car and she only makes short drives everyday (2 miles or so) so it never really works right for her.
Any ideas will be appreciated! Love this forum!
Thanks.

sorry that didn't work for ya, i'm really out of ideas then. Hopefully someone else will chime in here shortly. I know there are a couple of vacuum related sensors/switches that have a major impact on how the tranny shifts, maybe one of those is clogged or leaking. is your vacuum system in good opperation?
R

__________________
83 300SD.......sold
96 integra SE....sold
99 a4 quattro....sold
2001 IS300.......sold
2002 330i.........current.
2004 highlander limited....current.

Hey, thanks again, I guess I'll have to get a "real" shop manual, (no offence, Haynes) and go through all the vacuum system piece by piece until I find whats going on here.
Thanks again. Happy New Year.
Mike

Interesting problem.. I had the same exact problem with my 85 300D. It was late shifting into all gear with a hard pop for 1&2.

I decided this problem was above my talent and took it to my indy who adjusted the vac modulator on the transmission. It fixed my problems competely. I suggest the same for you.

Note when cold you will still have a stiff shift. This is normal. After my is at running temp 87C it shifts like a dream.

Thanks,

Morph

First, get a transmission oil and filter change, you betcha!!!
Haynes manual explains how to do it very well.

If the filter has been in there a while and is getting full, it could slow down the flow of hydraulic pressure, which would slow your shifts.

When you get the trans serviced like this, pop in a new modulator as well, they are cheap.(about $35 at the MB dealer). Just screws into the side.

But!! If you don't drain the oil first, and pull the modulator, you will lose a lot of oil outof this hole, so be ready!

__________________
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!"

Thanks you guys, for all your help here. I'm gonna do the trans fluid and filter next, even though the lady I just bought the car from said the trans was recently "rebuilt".
That could well be, but it reminds me of a guy who used to live next to the cycle shop I worked at, who sold "rebuilt" car engines. He always had people looking for him a day or two after they had picked up their freshly overhauled engines, and so after some investigation I found out his game: he would get a motor from the junkyard, sandblast it and put on a fresh coat of paint, then advertise as rebuilt!!! What a scam artist, boy, they sure LOOKED good.
So I will take your good advice on servicing the tranny before anything else, then check the other things mentioned as well.
Thanks again!
Mike

Well, I want to thank all who replied with helpful suggestions to my problem here, and what the shop has done is change a main vacuum line, plus the modulator, and now it seems the problem is in the vacuum control valve.(VCV). Fast Lane does not show it, nor does the other parts place on this website.
Now can anyone please point me to where I might find one?
Thanks again!
Mike

It is more likely your problem is the cheap 3 way valve on the top of the valve cover. The plastic finger wears down, and changes the calibration.
The modulator valve can be revived by a cheap new O-ring to seal it up again.

__________________
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!"

I had a similar problem with my 82 300D. It started practically giving me whiplash from first to second and clunking loudly when it downshifted. I took it to a great mechanic who replaced the aforementioned vacuum valve on top of the motor and voila! It now seems to be fine. It is still a little clunky when it is cold but much smoother when warmed up. Are all of these transmissions a little clunky? I know the new ones are computer controlled and ours are more primative but what is the best I could hope for? Even f I had the whole tranny rebuilt, would it still shift this way or would it be totally smooth?
The part was only $72 and had I known about this I could've easily done it myself but I was charged fairly.

__________________
1982 300D Turbo "Helga"
380,000 miles

Again, thanks , and I will be checking that switchover vacuum valve, as well as changing the VCV (if I can locate one, it has been broken by previous owner??)
I am presently awaiting the shop manual (on CD) from FastLane.
I also need to get a pressure gauge for my mighty-vac, I can see how much it would help with working on this car.
I have a hunch I should check the vacuum pump itself, what is the correct vacuum to look for?? Like 20?
All you who have been helping me out here, are greatly appreciated, and when the shifting is finally fixed, you will be the first to know!
Mike

Many things could be causing your problem, including a leak caused by a worn or loose line, transmission modulator, or possibly the regulator.....you would need to troubleshoot with the vaccum pump tool to be sure....otherwise it is a guessing game.

I had some rough shifting problems. My vaccum switches are leaking (there are two of them). For now I've plugged the line going to these switches until I can get a pair. It shifts pretty well which makes me wonder if I really need the switches...from what I can tell, at full throttle, one switch opens and pulls the vacuum to 0 to ensure a hard shift for a forced downshift. You definitely don't want a soft shift (causing wear) in this situation.

If you put a vacuum gauge at the line going to the transmission, you should see a variable vacuum reading with throttle position....I think mine varies from about 5 to 12 with the throttle.
(this is with the vacuum switch line plugged).

There is quite a bit of material on this forum you can search and study on the subject.

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D

Well, after 3 trips to the shop, it is working properly now, and what was done, basically, was replace leaky modulator, replace broken VCV,(very expensive!!), and finally re-route some vacuum lines in a way that now, the line going to the modulator tees off the TOP of the VCV, my head is still trying to see exactly what actually happened, and I don't know why it was so screwed up to start with, since I just bought it, but it does shift really nicely now, and I'm about as happy as can be.
Many thanks to all who participated in this mess, with the real fix being a combination of almost all your suggestions, you're all great in my book!!
Now, what is the most common cause of the heater not getting HOT when driving, but HOT when sitting and idling??