78 Mercedes 300D Transmission Bowden Rod Adjustment
 

I think I have read every thread out there about adjusting the linkages on the early w123's. But I can't seem to find a simple answer.

All the posts I've read talk about adjusting it, but nothing about the proper installation of it.

The transmission in my car was rebuilt in 2004 and then the car was parked. My problem is that the transmission doesn't seem to down shift wit the rpms nor up shift. I usually have to let off the gas to get it to shift at the right time, the kick down switch also doesn't seem to have any reaction.

Looking at the linkage running to the transmission it is pretty lose. I am thinking who ever reinstalled the trans linkage didn't install the arm in the right position.

So now my idea on how to confirm it is in the right location is to wire the throttle open, pop the linkage off the arm and see if it is opening what ever controls the shifting in the transmission all the way. If not remove the arm and put it in the right position....what's your thoughts on adjusting it that way?

Have you tried it with the kickdown switch unplugged? If not, try it now.

Nope, I was going to give that a try too! I have a lot of benz bugs I am busy working on so this ones on the list...just got all the fuses replaced today and the power steering fluid changed...though my nice clean fluid turned black again as soon as I started the car :mad:

I have one of these things in my 78. I'm guessing you are talking about the old automatic that had the rod modulator instead of the vacuum driven one? If so I have the FSM procedure for this.

Yep that's it, it would be great if you could post that. It should help me figure out the proper way.

If the switch is stuck then basically the transmission thinks you have the pedal on the floor and will hold upshifts for maximum power. It's something you should check.

Maybe you need to drain and refill that PS fluid reservoir too :D... sounds nasty.

Okay, I pulled the plug and it seems to be the switch. I still have a few hard shifts but it doesn't rev up like it use to...so now the question is how do you remove it?? I suppose it can be disassembled and clean too?

I've never pulled one. Generally speaking on a w123 by now everything in that area is caked in decades of grime buildup. I suspect if you clean it off, you'll find it screws into the floor.

If you want to pursue the shift quality any further, you are moving into the realm of vacuum. Speaking in simplified terms, the bowden rod controls the 'when' of the shifts. Vacuum controls the 'how', or shift quality, through a vacuum modulator located on the side of the trans.

The hard shifts are related to the working pressure of the vacuum modulator. First check that the vacuum line that runs across the rear of the engine, down to the modulator is actually there and is connected at both ends. If this is a yes, then you need a vacuum tester to check if its holding vacuum.

If that is a yes, then you can check to see if you are getting sufficient vacuum from the pump. You check that at the main vacuum line that bolts onto the brake booster with a vacuum gauge.

I've typed that as very general starter info. There are several extensive threads on transmission vacuum adjustment and there are lots of people on the board who have forgotten more than I know on the subject... so I will sign off here.

I run the cable pretty loose on my 300D. About as loose as I can get it safely.

Shifting early is a way to higher mpg.

He doesn't have a cable, the earlier cars like his have a metal rod that joins the linkages. There is no adjustment mechanism on the rod itself, as there is on the later cable setup on your '85.

There's also no vacuum on this one either. Just the kick down switch and rod.

I got the switch off, it just twisted out of the firewall. I took it apart but your not able to get to the contacts of the switch. I also can't seem to get it back black together. It is pretty gummed up with old grease and I believe it ran down into the contacts of the switch.

So where do I get a replacement at?

The newer ones I see in eBay don't lock into the fire wall like mine.

Hmmm. I had forgotten early cars didn't have a vacuum modulator... but my '78 Coupe does.

This your switch?
1978 Mercedes-Benz 300D Sedan - Automatic Transmission - Page 2

kickdownacharias;3091001]

This yours?
1978 Mercedes-Benz 300D Sedan - Automatic Transmission - Page 2[/QUOTE]

Nope this one is mine, cheapest I can find it...if you look you'll see two tabs...you insert it and then twist it to lock it in place.....I don't think I can find a way to hold the cheaper one to the floor board and can't for the life of me find a photo of that style installed in another 300d to see if there is a way to mount it on mine.....go figure that I would need the most expensive one.....I am ponder installing a dash mounted switch

1981-1985 Mercedes Benz 380SL Kickdown Switch - OES Genuine W0133-1618189

http://cdn0.autopartsnetwork.com/ima...1618189OES.JPG

There was actually a thread about the swtich last year... not everyone's a fan of the floor setup. Someone came up with an idea for a switch on the shifter with the wires running down the shaft. You could try some searches and see if you come up with anything.

Don't know about 78 but the 77 I had the adjustment was to have some one floor it to just before you hit the switch and the loosen the tighten the adjustment rod under the exhaust manifold from underneath