I have a 123 chassis 1984 300TD that has been downshifting real hard and not too smooth in other gears. I have replaced the levers on the 3 way vacuum valves and changed out all the connectors. Still shifting hard, so then I checked the vacuum system. With the car running the vacuum gauge registers 22 from the supply lines. The problem is with the three way connector that goes to the dashpot. The only end that I get a zero reading is the supply end that connects to the dashpot that feeds to the transmission. I've even turn the 3 way connector around thinking maybe it was just that end. Doesn't matter, it still reads zero.