The modulator can be a little tricky to replace. If you don't pull it straight out, there is a plastic "pin" that can snap off. (Don't ask me how I know) Depending on where it breaks, you may have a major disassembly on your hands.(Fortunately, 90' needle nose retrieved mine.) If it is holding vacuum, I would check for vacuum leaks in the rest of the system first.

Changing all of the flexible connections ($10-15) cured the shifting problems I had.

__________________
Sam

84 300SD 350K+ miles ( Blue Belle )