83 300d shifting problems
 

My 83 300d experiences very different shifts when it is cold and when it is hot. My fluid level is good so I dont think that has any bearing on the problem. When it is cold outside (roughly 40 degrees F and below), the trans doesnt want to shift until 3500rpms or more, and when it finally does it shifts hard. Sometimes it will not get past second or third, and you have to quickly shift into neutral and back to drive for it to shift to the next gear. Yes, I break torque to do this, so dont get the impression that i am drop shifting my benz. Once the car has warmed up, (15-20 mins of normal driving) it goes back to shifting like normal. Another way that you can make it shift into forth is to very quickly blip the throttle heavily, and it will sometimes shift. I havent checked vacuum levels to trans yet, but I have no idea how temp would affect the vacuum. Any help or ideas would be greatly appreciated. THANKS!

GLIDEHM

VCV controls amount of vacuum sent to transmission based on the rack position. Shift points are controlled by the bowden cable, also controlled by throttle linkage. A cold diesel has less horsepower so you have to push the accelerator harder to get the same power. So, the VCV and bowden cable interpret the deeper foot as a demand for more speed and more rpm's and higher shifts.

I dont think that lower amounts of power are the culprit. The reason that I say this is because the car is always plugged up, and when I do crank it up, I allow it to run for at least five mins or so before I start my drive. By this time the coolant is prob 70 to 80 degrees C. Im a very attentive driver, and I travel the same roads every day. I know I'm not providing any more throttle input when the car is "cold" versus hot in order to achieve the same conditions. And it still doesnt help to explain why sometimes it will not shift into fourth gear, even if you take it to 4000+ rpms, which i do not like doing on a regular basis. I greatly appreciate your input, and I'm gonna give your ideas some more thought. Thanks!

You need to read Kerry's response closer. If you understand the fundamentals of the transmission (I'm not saying that you don't) then you can assure that your transmission controls are adjusted correctly. Once everything is adjusted correctly then you can diagnose the problem better.

Also, If 15-20 minutes of driving is making it shift better, then something whether it is the engine, the transmission, or both is warming up. It may seem as though you aren't giving the car more throttle when you first start driving due to it being cold, but just the slightest bit more throttle can make the vcv decrease the vac to the transmission. I think that if the cable and linkages are out of adjustment, the results of the small amount of added throttle could be more pronounced.

Also, when you say plugged up are talking about a block heater or a coolant heater?

Another idea is that you have restirctive flow of transmission fluid. When the trans heats up the fluid moves more freely making the car shift normally. But then again this is a guess that may make sense once you have confirmed that your trans adjustments are correct.

On my Car for a while I had no shift into First Gear at all unless I reved the Engine. It would also not go into First Gear. The above started during the 1st couple of days of some Cold Weather.
It appeared to be a B2 Piston Issue. I did not have time to fool with it so the Car was driven starting in 2nd Gear; shifted there Manually.
When I had time to do so I changed the Trans Filter and now everthing I now have a 1st Grear and everthing seems as it was. The Weather is also slightly warmer also.

It may seem unlikely to start troubleshooting with a Fluid and Filter change because the chance that it will help appears small. But, it rules out a possible source of a problem.

Some of the stuff I read indicates it could be a Transmission Modulator Problem. But, again as the others said you still have to make sure your other adjustments and that the lines are not restricted in order before fooling with it.
You might take a look at the Cap on the Modulator. Perhaps there is a Crack in it the Cap that causes problems when cold.
An article on adjustments:
http://www.continentalimports.com/ser_ic20242.html