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1979 300D questions

5K views 4 replies 3 participants last post by  cracker928 
#1 ·
First, what transmission fluid should I use? It is an automatic.

Second, were there ever 300Ds with manual transmissions?

Third, were is a good place to get a shop manual for this car? Just ask the dealer?

Fourth, what is this Fuel Enrichment System? The car has weak power on inclines, etc.

Seems to run o.k., but doesn't like the 2/3 shift (or maybe 1/2).

Thank you!
 
#2 ·
Welcome :)

In response to your question about an shop manual, I have seen some manuals on CD being sold from time to time on eBay. Also, if you need an owners manual you can get a replacement manual by calling the publications department at MBUSA. For a fee they will send you a new (reprint) manual for your car. You can reach Mercedes-Benz at 1-800-FOR-MERCEDES (800-367-6372). If you look in the Resources page on our site you will also see a link to the MBUSA website. Good luck and welcome to BenzForum.
 
#3 ·
Welcome!

Mercedes seems to only recommend mercedes brand with no clues as to what is compatible. I have been running Dexron/mercronIII in my rides, as many aftermarket manuals suggest.

I believe all US spec 300D's were automatic, while euro-spec cars commonly had manual transmissions.

The fuel enrichment system primarily applies to turbo, where the air charge is highly variable, and therefore the fuel/air ratio must be changed to optimize performance. I am sure that the normally aspirated cars have a similar system to compensate for altitudes and weather, but with far less impact on performance.

If you are having performance issues, the first steps with any diesel are to make sure the fuel system is running clean and there are no vacuum leaks. Fixing these will cure the majority of the issues that diesels have. Of course, make sure the air filter is clean and that the vacuum pump is functional.

E-diagnsing transmission problems is very difficult, as they are not much better in person, but please try to elabrate on your shifting problems.

HTH,

-Neil
 
#5 ·
There are two things that lead from the engine to the transmission. One is a vacuum line that goes to the modulator controls the shift quality. The other (which should be the one you want to play with) controls the shift points. This cable is called the "control pressure cable" or "bowden cable" depending on who you are talking to. Anyway, the tighter the cable, the higher the shift point. It can be loosened by lengthening the rod (an easy screw ajustment) that the cable connects to the throttle controls on the engine. Small adjustments can make a big change, so be careful to make the current adjustment as a reference point. Try 1/8th to 1/4 inch increments to start with.

Hope this makes sense, and let us know how it works out.

As an aside, if this cable ever breaks, the transmission will upshift at about 2000 RPM (way too early)

-Neil
 
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