My 85 300SD that I bought a few weeks back suddenly does not
want to upshift from 3rd to 4th. The only way for me to have the
transmission shift into 4th is at highway speed drop the transmission into N and then drop into D and this drop it into 4th.

The shifts from 1 to 2 to 3 seem to be a lot more jerky then before
and the shift points are lot higher in RPM.

I look forword to your suggestion and comments.

Thanks
Venkat