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Old 08-05-2010, 03:41 AM
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Join Date: Aug 2010
Posts: 2
Mercedes 190D transmission problems due to Vacuum??

I bought a Mercedes 190D 1 month and a half ago and I have been putting all my effort to put it back to its original standards. Couple days ago the transmission was rebuilt by a friend and I. Before that was done I had lots of problems when shifting.. early shifting on it, and it still does it.. When you are rolling at 20MPH it's on the 3rd gear already.. by the way.. the 4th gear doesn't works?.. or I think so.. since I haven't noticed when it shifts to 4th..

The transmission work was pretty good repaired, my friend is a transmission mechanic. I've read on this site regarding the vacuum.. vacuum could be all the problem. I tried to adjust the Vacuum Modulator but it just makes a little bit late shift, not as should be, and the transmission kicks (when upshifting).
I don't really know how to start checking.. how can I test if the vacuum pump is working. Oh.. I disconnected the vacuum that goes to the valve where the air cleaner goes and it's a good vaccum pressure.. What else should I do to check..

I hopw you guys can help me out.
Thank you so much.
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Old 08-05-2010, 05:05 AM
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Join Date: Nov 2009
Location: Victoria Australia - down under!!
Posts: 4,023
Welcome to the forum !!
Best that you dont touch the modulator until you establish that you have good vac there first!!
Would be useful if you could put a pic up of what you are refering to near your air cleaner.
When you get a chance, could you put some details about your car in your signature so that we no a bit about it.

Good luck !
Grumpy Old Diesel Owners Club group

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1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
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Old 08-05-2010, 08:00 AM
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Join Date: Dec 2003
Location: Festus MO
Posts: 762
What are your rpm's at 60 mph? Are you sure it's in 3rd, and not in 4th?

It is more likely that you are not getting 1st gear, and that it's actually starting in 2nd, then shifting to 3rd and 4th.

'93 190E/D 2.5 Turbodiesel 5-speed (daily driver)
'87 190D 2.5 Turbo rustbucket - parts car
'84 Dodge Rampage diesel - Land Speed Record Holder
'13 Ram 2500 Diesel
'05 Toyota 4Runner
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Old 08-06-2010, 03:23 AM
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Join Date: Jul 2010
Location: Hamilton Ontario Canada
Posts: 394
I just picked up an '86 190D a month ago. It had very poor accelleration and shifting way to early. The Bowden cable (cable from the trottle to the transmission) needed adjustment. On mine there is a sliding adjustable linkage between the throttle and the bowden cable. I had to tighten the adjustment up almost as far as it would go. Now it shifts on time.

I had the same concerns about not getting into top gear. Turns out it was in top gear, I was starting off in second. This is normal by the way. The transmission will only go into 1st if the signals it is getting tell it to.

There is a switch on the floor below the throttle pedal. It delays shifting under full throttle. The pedal did not touch the switch when pushed to the floor. There was a piece missing off the switch. I clamped a spacer to the throttle pedal and now it hits the switch.

Adjusting the cable made the biggest difference in shifting. It fixed my acceleration and not going into first gear.
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Old 08-10-2010, 05:00 AM
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Join Date: Aug 2010
Posts: 2
Smile Thx

Thanks for your comments guys!
Ok here's the thing.

When I accelerate from a full stop it starts shifting early, @20MPH i'm already on 3rd gear and it makes it to be really slow (I feel is the 3rd gear since), is like when in a stick shift car, If you start on first and then you go to 3rd instead of 2nd it takes time to accelerate until you go faster.
I tried to do some adjustments on the vacuum modulator but it doesn't work, it just makes a liiitle bit difference but then it shifts harder.

Also I don't know if my kick down switch is ok.. I tried to press it with my hand while the car was turned off and I can push it and then it pops back , I don't know if by pressing the accelerator it activates it (I dont remember if I checked that the last time) but anyways it doesnt works or makes any effect while driving..
I tried to adjust the linkage over the valve cover but I don't feel it makes any effect.
While driving at 65MPH my revolutions are 3500 but I think it needs like a 4th speed..

I hope you guys can guide me to make those adjustments. Tomorrow morning I will take some pictures and post them here. Also the pictures from the part which is just moving around under the intake manifold.

Here are some of my car..
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Mercedes 190D transmission problems due to Vacuum??-img_2218-1-.jpg   Mercedes 190D transmission problems due to Vacuum??-img_2084-1-.jpg   Mercedes 190D transmission problems due to Vacuum??-img_2222-1-.jpg  
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Old 08-10-2010, 07:31 PM
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Join Date: Jul 2010
Location: Hamilton Ontario Canada
Posts: 394
I am pretty sure at 3500 rpm you are in 4th. These transmissions default takeoff gear is second. Stop messing with your modulator, this will not change when it shifts, just how hard it shifts. Is the cable hooked up correctly to the transmission? This is the direct link to the transmission from your throttle. If anything, this is your problem. Tighten it up as much as it will go and try that.
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