1983 Mercedes Benz 240d shifting point

you can try changing the vacuum modulator valve, but before you do that make sure you are getting vacuum to the vacuum modulator, also has a throttle body pressure adjustment which is on the right side of the firewall it is a cable that goes into your transmission. When is the last time you service the transmission?

Your transmission is also probably suffering from old age and neglect. At this point, it makes sense to nurse it back to health. Check the valve as suggested above. I bought a 1983 also, and it suffered from neglect and sitting unused. I would also do the following... Go buy Lucas Transmission Fix, a 24 oz. bottle. If you are uncertain about this go to the Lucas and read all of the testimonials. Pour about 18 oz down the dipstick tube. This must be done very slowly while the engine is running. I drove away, and I have had no slipping since. What you have done is a fluid modification. You probably have not changed the fluid or filter I am guessing. Drive this way for 2-3 months, and go buy a Mityvac fluid transfer pump. Drain as much of the fluid you can using the Mityvac. This is also done through the dipstick, BUT with the engine turned off. Get your manual out, and fully understand how to read your dipstick. There are exacting instructions, as this is important. You do not want to overfill or under fill. Pour a half bottle of the Lucas Transmission fix in first. Check how much fluid you drained, subtract out the 12 oz you just put in. If there was not much fluid in the Mityvac, you were probably low. Check your manual to see the capacity as ONLY a reference. Gradually add the correct trans fluid, and keep checking it. Check it the next day again. Drive the car for another 2-6 months, and this time fully drain the trans from the bottom, and replace the filter. DO NOT WIPE OR TRY TO CLEAN THE INSIDE OF THE TRANSMISSION. THIS IS THE KISS OF DEATH. Any small bit of lint will probably destroy the trans. CAREFULLY wipe and clean only the edge where the gasket goes. Use nitrile gloves (buy a box from home depot for $13). Replace the filter. Check the gasket area so it is totally clean, and replace pan. Torgue correctly. For $12 you can subscribe to www.epc.startekinfo.com which is Mercedes website that shows most all of the Mercedes parts diagrams for all of their cars. Search in the MD mode, and find your car model, which is a 123123 Japan and US. You can also subscribe to www.alldatadyi.com for $26 1year or $46 for 5 years. I believe this has most of the torque settings for your car.

DID YOU FORGET TO PUT THE FLUID BACK IN YOUR TRANSMISSION? Add about 18-20 oz. of the Lucas Trans Fix first. Then gradually add and check the fluid level. When you drain the trans this way, you do not get all of the fluid, as some is left in the torque converter. This is an old car. I don't think I will ever have a power flush done on my transmission for fear of jostling something loose which could clog a valve or something. There are not too many people left in the world that know how to fix these cars, not even the dealers. Most of their technicians were toddlers when this car was released.