On a 1983 MB 300 SD what could be wrong when the downshift upshift is rough and fluid level is ok?

Answer 1

it sounds like a vacum issue, get a manual or have it serviced n0rt The vacuum issue took me to further findings. Besides improving the vacuum lines, I also got a tip that worked very well: Adjusting the Control Pressure Cable. It is located on top of the valve cover where several other connecting rods are, near the backside of the valve cover where the Mercedes star is. The control pressure cable is the one that is packed into an approx. 3" long, black rubber wrapping. What you do is you pry off the ball socket. Use suitable tools that aren't too rough on the ball socket and head. You might need to twist and crank it quite a bit until it comes apart. Once it's apart, you push the ball socket backwards (in the direction where the cable goes) and then pull it slowly forward until you feel a slight resistance at one point. Don't move it any further. If you miss, repeat as many times as needed until you got that point. Now adjust the control pressure cable with the adjusting screw that is located right behind the cable holder until the ball socket is exactly above the ball head. Attach the ball socket and the ball head in this position. It might be a good idea to note down how many turns you had to adjust the cable so that you could go back to that setting if shifting worsens (in case your vacuum system is way off and the cable setting maybe was done intentionally to compensate). This procedure seems to be appliccable for all MB turbodiesel 1981 to 1984. It improved shifting on my 1983 MB 300SD tremendously, and it is now practically all smooth up and down. Before, I expected the tranny to come apart any time of shifting. I also found an excellent article "Mercedes-Benz Transmission Vacuum Control system 'Tuning'", by Steve Brotherton at www.mercedesshop.com/Wikka/TransVacTune.