New to forum; Have missing linkage + transmission shift issues on 1978 300d

[DieselDog]

Hello,
First off, I would like to say that this forum is great! I love it, and I am a regular lurker, but just joined up today. I own 2 jetta tdi's and I just recently aquired a 1978 mercedes 300d. In the past I have owned a 1985 300d Turbo (was my favorite car of all time) and I have also owned a 1982 240d manual trans (I also loved this one, it was stingy on diesel). Anyway, the reason I am writing is I hope some of you can shed some light on a couple of the issues I have on the 1978 300d. The engine seems to be in great shape, the body has zero rust, and the trans seems ok as far as the fluid looks good, and it is not leaky anywhere. The issues are this. I am fairly certain the throttle linkage in its current state is missing some of the mechanism. I have to use a generic throttle spring I bought at pep boys, rigged up to bring the linkage back to idle when I let off the foot pedal, or the pedal will stay down. I am sending some pictures, it looks different than my 1985 turbo did, and I dont know what I am missing. Maybe some of you can tell. Also, in relation, my shifts are late and hard. I mean I know all auto trans 300d shifts are harder and sometimes a little later than normal cars, but this seems excessive. I cannot for the life of me locate the transmission vaccum modulator on this model. It is not where it was on my turbo 300d or where the pictorals of the 300sd on the diesel giant website show it. Can any of you shed some light on this? I think it could be the reason for my later and harder shifts. Thank you all for your time and keep up this awesome forum! -Ken

Pics:
http://i327.photobucket.com/albums/k469/kendawg100/300d1.jpg
http://i327.photobucket.com/albums/k469/kendawg100/300d2.jpg
http://i327.photobucket.com/albums/k469/kendawg100/300d3.jpg

[DieselDog]

Bump. Anyone?

[rs899]

Can't help you much with the linkage (since I don't have an early W123 300D) except to say that it's not right.

I think your car may well have had a mechanical modulator. Do a search- I am pretty sure it has been discussed a little.

Rick

[vstech]

I have a 78, 79 and an 80, I will take pics in the morning...

[vstech]

here is a pic of a N/A 616 I think, I got it helping somebody here on the forum... it may help...


there is a lot wrong in this pic, but I think the linkage is the same as yours should be.

nope, my 79 300TD has another rod that goes accross the valve cover and down by the exhaust manifold... ignore the pic. I will get correct pics in the morning, or sometime tomorrow.

[yellowbenz]

Here are some pics. Evening so not so great. If you need more or different views let me know. Circled the adjustment rod. As I recall from previous posts, lengthening the rod will bring on the shift at lower rpm. It helped my hard, high rpm shift from 2 to 3.

[yellowbenz]

I don't think the linkage looks any different except for the added spring. I wonder if the problem lies with the accelerator pedal assembly? Does the throttle linkage bind?

[DieselDog]

Whoa, thanks for all the response guys. I have been messing with it on and off tonight and got back to these great responses. It seems like Rs was right, it is no doubt mechanical, and I did find some old threads about locating and adjusting it (somewhere behind the tranmission, drivers side) but I was kind of unclear on exactly how to do so and what the proper parameters were. Yellowbenz, those pics are great man, exactly what I needed, I guess I'm not missing anything. That one "open" ball looking connection in the back had me thrown as all the others are connected. Theres a heck of a lot more going on with the newer ones in that area, and I guess my memory just threw me off because I have never dealt with one this old. Anyway to answer your question, yes the linkage is binding, somewhere between where you circled that adjustment rod and the trans (or so it seems). I dont think the pedal is binding just not snapping back into idle when I let my foot off. If I take that "half" of the linkage out of the picture, it seems nice and loose. I'll probably just get the ramps out and try to figure it out by following it back to the trans, and lubricating as I go. Still unclear on the mechanical modulator behind the transmission from earlier posts, do I make the major adjustment there or the rod you circled or both? Anyway, thanks again, vs, rs, and yellow. You guys rock! -Ken

P.S. This thing is SLOW. I know all NA engines are, but will a diesel purge and a valve adjustment give me some more acceleration / power? It seems like it wants to rip, but that its being held back. Even my old 82 240d 4 cylinder seemed more powerful, I guess thats because it was stick though. Dunno.

[MB-Owner-in-ind]

My '77 starts off just as fast as the '83 turbo but doesn't have the extra power at 2000 rpm and above. Lubricate your linkage with white grease and after it is freed up then check the full throttle setting.(do a search for procedure or buy a Haynes manual. The adjustment for the transmission is located under the intake manifold and again the Haynes manual will tell you how to make this simple adjustment.

[vstech]

for a binding linkage problem, look under the air cleaner. the linkage gets pretty close to the exhaust manifold, most are totally devoid of lubricant, and will bind here, take it apart, spray with pb blaster, and brush clean, then lubricate with some high temp brake grease! world of difference!
this alone is probably the most significant reason for the changed throttle arrangement on MB's...

[kerry]

As far as I know, the non-vacuum controlled transmissions in the 123's are adjusted with the aforementioned rod system and there is no mechanical adjustment on the driver's side. I may be mistaken.
If that linkage is binding, lubricating it may solve your problem without any adjustments.
My 77 300d was pretty doggy too. It is designed to start in 2nd gear. It was a little more peppy if it started in 1st but nothing like a turbo model. I do live a mile high.

[yellowbenz]

1978 300D Transmission (non-vacuum) modulator adjustment

This thread might help explain the transmission adjustment.