I have a 1990 190EE 2.6 and just today, my shifting has been horrible. It seems like the shift goes immediately from 1st to 2nd to 3rd. And even if I put the gas pedal all the way to the floor it slowly climbs up from 20 mph to the normal speed limit which is 40 mph. I read several posts on here and they all seem to point towards a vacuum modulator, but I dont know where it is or what it looks like. If you have pics, that would be great too. Thanks guys.

or maybe it isnt a vacuum modulator, but something else. Not sure, please advise

Got your PM, here is the answer.
I would need your VIN# for correct part.

Transmission:
Transmission:



Have a great day.

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1985 300SD
1983 300D
1984 190D
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https://www.boldegoist.com/

As per your VIN# the part is MB# 126 270 25 79.

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hey, thanks, im still trying to figure out that pic though. im guessing the best way to approach this would be from underneath with the car on jack stands. am i in the right area by checking the modulator or would there be another cause for my shifting through all 4 gears before the car even reaches 10-15 mph?

Possible bad "kick down" switch.
MB# 002 545 22 14
http://catalog.mercedesshop.com/item.wws?sku=W0133-1626222


Under the accelerator pedal...

Did you check the Bowden cable? It might have come loose, and that is what affects shift vs. throttle position.

Steve

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'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7

whunter- I found out where the kick down switch is under the gas pedal. I was able to disconnect it and look at it. It has a small black cap on top of it and I am able to depress it, but I have to put moderate pressure on it....like stapling 10-12 sheets of paper (that kind of pressure) is that normal? I also had it disconnected and decided to drive around in my parking lot and noticed that I still would cycle through all 4 gears at 17-20 rpm and still be under 20 mph. So no change with it off either.

sbourg- How do I check the bowden cable? I'm assuming the cable with the white nut that you are able to twist that sits under the air filter. I did remove the air filter cabin and there is another cable that if the car is on and you move the metal piece attached to it, it revs the engine. (sorry, I'm not too familiar with the names, just certain parts and what they do). Anyways, I noticed that when I moved the piece it was slightly sticky, not much though. So I srayed the movable parts (hinges and cables) with WD-40, they move more freely now, but I took the car for another test drive around the lot and nothing. I did not check to see if the Bowden cable came loose because I don't know where the other end terminates at. It disappears behind the firewall somewhere.

My transmission started shifting through all 4 gears when I accelerate from a dead stop within 5-6 seconds of acceleration and the rpm stops at 20 and I'm still going 10 mph and no matter how hard i step on the gas the car slowly crawls up to speed.
Well as I was looking under the hood, I found this vacuum line (see pics).
The rubber elbow was connected to the small metal part circled in the picture, its hard to see but it is right next to the valve body.
Anyways, it was the only vacuum line that I saw that may possible be related to the transmission so I disconnected the rubber elbow part and slowly began to pull the line to trace it to the source and lo and behold it was disconnected from wherever the other end goes.
I traced it down somewhere past the oil filter, or somewhere in that area. Bad news is I have no idea if this is the source of the shifting problem or not.

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Not really understanding what your trying to explain i will say this about the symptom

UPSHIFT too soon all gears --

the Boden cable ( downshift cable USA ) controls the when a trans shifts in a MB and the modulator determins how firm the trans shifts gears

My guess the boden cable is broken or has come un hooked < the first thing i would check than post again - jz

Yes, upshifting too soon, I was able to track down bowden cable and it is fine. But what about this vacuum line I hav e. Where does it go?

combine post #2 and #3 with this attached picture to restore vacuum to the transmission.



Note:
Do not make multiple threads on the same issue.
Moderators can change your thread title on request.

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Sorry about the multiple posts. So the one end goes on top where it is circled and the other end goes on the vacuum modulator? Do I have to disassemble anything to get to the modulator? I just went and bought 2 ramps to elevate my carb so I now have a little access underneath....

NO.
It is all external = connect the hose on each end, and you are done.

Sorry for beating a dead horse, whunter, but what you are telling me to do is to reconnect that rubber elbow/vacuum line to the metal end fnext to the valve body ( as in the pictures I took) and then just plug up the other end of the vacuum line?

Post #2 shows a picture of where the other end of the vacuum hose must connect...

One end connects to the intake manifold.
The other end connects to the VACUUM MODULATOR.