I have a 116 (78 300sd) and will take a look at this.

Question - sometimes my 116 will seems to slip a little between 2 & 3rd gears. It seems that this tends to happen with moderate load on the engine. When under heavy load and light load it tends to be more normal.

This is a tranny going bad or a vaccum problem . The tranny shifts real smooth all other times.

PS - Fluid level is fine and filters are routinely changed.