I had a 727 in my dart with reverse/shift, manual shift vave body (sox and martin). In drive (old first gear posistion) it would only shift auto from a stop. Any downshift would have to be manualy shifted to include what you call passing gear. That's why they call it manual shift. There was no detent/downshift cable! Don't know if this applies to the TH350 though, that's just the way it was in mine.