Does a 1981 300 D have a bowden cable ? - PeachParts Mercedes-Benz Forum

RichC · #1 12-16-2005, 08:33 AM

My transmission has the quick shifting and flaring problems. I have been reading what I can find on the forum about solving these issues with vaccum and boden cable adjustments.

I cannot seem to find the bowden cable on my 81 300 D.
If there is one, where is it ?

The previous owner has the vacuum line that runs to the transmission connected directly to the first T off the main vacuum line that runs from the vacuum pump to the brake booster. Is this correct ?

Ara T. · #2 12-16-2005, 08:35 AM

It should, it is atop the valve cover, all the way on the end closest to the firewall. Just look at all your accelerator linkages and you'll find it, its the short one with the rubber boot and has the little cable running out of it.

RichC · #3 12-16-2005, 10:30 AM

I just cannot seem to find this cable on my car.

I have one cable running to the little adjuster on the dash that I assume controlls the idle speed.

and another running to the canister on the driver side fender that i assume is the cruise controll actuator.

where does the bowden cable connect with the transmission ?

pawoSD · #4 12-16-2005, 10:41 AM

I believe it goes along down the drivers side of the tranny and enters towards the top. On top of your throttle linkage on the valve cover there should be a black sheathed cable with a white/beige "screw adjustment" thing with a rubber flexy boot on it. If it is missing that would account for some shifting issues!

Phil · #5 12-16-2005, 11:01 AM

Look in the DIYs at the top of the page under basic transmission adjustment.

RichC · #6 12-16-2005, 12:00 PM

I will see if I can find the end connected to the transmission. And hopefully find the other end that goes to the throttle linkage by tracing it up.

I have a feeling it has been removed or has been jammed up somewhere between the transmission and the body

The vacuum lines have been messed with also.

The vacuum line that goes to the modulator connects directly to the main line off the vacuum pump. I do not think this is correct.

I think I will stop calling this a project and start calling it an adventure now

RichC · #7 12-17-2005, 12:21 AM

Yep, I'm pretty sure the PO removed the bowden cable.

I found a plastic connector on top of the transmission near the engine that connects to nothing and looks as if it was broken off.

I am suprised the transmission shifts at all.

The peice is black plastic and has a 90 degree angle to it.

Does anyone have a picture of this cable at the transmission end so I can be sure that it is the bowden cable ?

And if anyone wants to sell a cable and the linkage It looks like I'm in the market to buy one.

Thanks for your help.
RichC

pawoSD · #8 12-17-2005, 12:39 AM

I don't have a picture at the transmission end, but this is what it should look like on top of the engine. Note that this pic is of a massively disassembled engine bay (I'm workin on it....

).....but the bowden is still there, the little adjustment screwy thing is right underneath the breather tube I have laying there where I circled the smaller circle....hope this helps. As far as I know it connects to the drivers side upper area of the tranny.

romansek · #9 12-17-2005, 01:33 AM

I have a 1981 300D and this model does not have a bowden cable.
You need to check the vaccum at the transmission modulator valve. I had a similar problem and adjustment to the valve solved it.

Good Luck

RichC · #10 12-17-2005, 02:41 AM

I guess I need to check and see if this is the origional transmission in this car.

Thanks for the picture. The throttle linkage looks somewhat simmilar to mine ( except for the cable of course).

I do have the vacuum regulator connected to the top of the IP that is supposed to supply a regulated vacuum leak to the transmission modulator, but it has an extra vacuum leak at the throttle linkage shaft.

There are two vacuum ports on the regulator. I am guessing one is for the connection to the transmission and the other is for connection to a vacuum source, and that there should not be any leaks between the two. Is my thinking correct here ?

How sensitive are the adjustments to the modulator on the transmission. Should I try a quarter of a turn or several revolutions ?

Thanks again for the help.
mutch appreciated.
this is a great group of people.

paulem · #11 12-17-2005, 11:46 AM

I have the same car...I rnr'd the engine and (have to pull the trans as well) and mine does not have a bowden cable, or any place on the trans where it like like anything isn't connected.

Something is goofy about my trans though, the car doesn't shift until it sounds like the engine is about to explode, and when it shifts, it chirps the tires. Obvisouly, I don't drive it in this state . . . I figure I'll wait for a warm day (its -3 with wind chill right now) to try and figure it out. I bought the car with a bad engine, so I don't know how it shifted before I started tinkering . . .

Can this be cause by vacuum modulator issues?

Eric

RichC · #12 12-18-2005, 01:48 AM

It looks as if we may not have bowden cables on the 81 300 D's

Through my experimentation with different levels of vacuum to the modulator on the transmission. I have found if there is no vacuum at all to the transmission I will get one shift from first to second at a very high rpm with a chirp from the back tires, like yours is doing.

The previous owner connected the vacuum line directly to the main vacuum line coming from the vacuum pump. Bypassing the vacuum regulator connected to the top of the IP pump. This gives me very low rpm shifts through all gears with a very light foot on the gas. If I press any harder on the throttle I get flairing ( sounds like the transmission hits neutral )

I hope this at least gives you somewhere to start tuning your transmission.
RichC

pawoSD · #13 12-18-2005, 02:00 AM

I think your right that the 1981 300d does not have a bowden cable, at least it didn't from the factory.

When looking through the transmission parts listings on fastlane, the replacement cable is absent from the 1981....which was quite different than the 82 onward ones, as that was the year it went turbo, and thus had a different tranny (with a bowden cable).

However, if you do not have the original Naturally Aspirated 5cyl and tranny, but have a transplant turbo motor and tranny, you would definatley need the bowden cable.....

RichC · #14 12-18-2005, 04:47 AM

I did not think of checking Fast Lane. Thanks.

When adjusting the modulator on the transmission should it be turned multiple revolutions or just a few degrees ?

Thanks
Rich

pawoSD · #15 12-18-2005, 06:17 PM

Adjust it one "notch" or two at a time, full rotations = huuuge adjustment. I think I went 3-4 clicks to achieve a much firmer shift.....