Linkage Operation / Bowden Adjustment : 1985 300D - PeachParts Mercedes-Benz Forum

300Drestoration · #1 05-22-2017, 12:50 PM

I'm a bit confused about the physicality and/or movement of the linkage in relation to the bowden cable.
I have some shifting issues, the most obvious being that it stays in 1st gear too long until it finally shifts.
So experimenting with the bowden cable seems something to try, however i am confused about how the linkage relates to the tension of the bowden adjustment.

I tried adjusting the bowden cable in both directions but it didn't affect the timing of when 1st gear shifts into 2nd. I understand that this usually means the problem lies elsewhere, but i at least want to make sure my linkage is operating correctly..

My concern is that there is quite a bit of loose play at one hinge point before the linkage catches this bowden hinge point. Shouldn't this hinge be resting in direct contact with the rest of the linkage so that when the accelerator is pressed the linkage starts to immediately pull on the bowden cable?

Should i be tightening the cable until that loose moving segment lines up with the linkage? Or is this loose play actually a providing a function of physical delay which is part of the overall adjustment, and maybe it is necessary for there to be some gap there in the initial action?

https://dl.dropboxusercontent.com/u/4482480/IMG_5159.mov

300Drestoration · #2 05-22-2017, 08:28 PM

I adjusted the bowden cable so that the whole hinge point is not loose and the balance between tension and resting point is where i believe is correct. There is no longer any play with that extra hinging mechanism in video above.
Previously i had adjusted the bowden cable one full turn inwards and then one full turn outwards, with test drives between, and after no results i did it two full turns in and out with tests between again. No improvement in shifting out of 1st gear sooner. Still rev'ing way to 3000 rpm or above before shifting.
So i assumed that the cable had been misadjusted in the past and set it up how i believe others have been saying it should be. Was hoping this would then change things since apparently the adjustment had been in a weird spot all along but still i got no change in my shifting.
I wonder if since my bowden adjustments have zero impact on shifting this means that my transmission is truly out of whack. But i am of course hoping that this isn't necessarily true and that other shifting issues still play into the situation such as the vac system.

optimusprime · #3 05-23-2017, 05:03 AM

Adjust the nut on the cable and note how many turns you give it .So you can put it back in the same place after if you dont notice any change .But also check oil before you do any work on the cable .Get engine up to temp ,then an a flat ground put it in park with service brake on , and with engine running . Pull out the dip stick wipe it clean with lint free rag [most important] so no fibre of the cloth gets inside the transmission. You shold have high and low on the dipstick to fill up to if its low .Never over fill the transmission if you do remove some to the right level .

300Drestoration · #4 05-23-2017, 08:30 AM

Quote:

Originally Posted by optimusprime

Adjust the nut on the cable and note how many turns you give it .So you can put it back in the same place after if you dont notice any change .But also check oil before you do any work on the cable .Get engine up to temp ,then an a flat ground put it in park with service brake on , and with engine running . Pull out the dip stick wipe it clean with lint free rag [most important] so no fibre of the cloth gets inside the transmission. You shold have high and low on the dipstick to fill up to if its low .Never over fill the transmission if you do remove some to the right level .

Thanks but yes i did go through the process of getting this vehicle back to an acceptable trans fluid level a few days ago. It had been so low that it required nearly two liters. I was very through and patient with the increments at which i added, and using good operating temps and shifting around between additions. I picked up this car with very little knowledge about it's recent history.

Also, the trans oil did not seem burnt at all.

300Drestoration · #5 05-23-2017, 09:12 AM

If bowden cable adjustment changes nothing at all about my shifting performance, what realities am i facing? That the transmission guts are where the issues lie?
Or is it possible that the transmission could be in decent health and that there are in fact other shifting related segments needing the most work..?

In other words, I know that the vacuum system is the other contributer to shifting besides the linkage/bowden, but i haven't figured out if this is a major red flag if the bowden cable adjustment does nothing.

I am facing a lot of overhaul which is all well and good and will be a solid summer project but i'm also curious about zoning in on prominent issues to perhaps make some order of priority.

There is tension in the bowden line and it springs back when i pull and let go.

ROLLGUY · #6 05-23-2017, 09:57 AM

Sounds like maybe not enough modulator pressure? You could try to tighten the "T" under the rubber cap of the modulator, and see if that changes anything. It also could be a sticking governor. I have heard that doing a complete fluid and filter change, frees up mechanisms inside, and fixes some problems. It may not hurt to do a fluid and filter change if for no other reason than knowing it is fresh (especially if you don't know when it was last changed).......Rich