Remember this with shifting action on the 300sdl transmission:

High Vacuum equals soft shifts

Low vacuum equals Hard shifts.

My 300sdl had a very soft shift, almost a slip between 3 and 4th. I disconnected the electrical connection to the device that boosts that vaccum when the engine is cold. Now my shifts are a little firm when the engine is cold, but I like it that way.

At normal operating temp, my shifts are just perfect.

John
1986 300sdl