Have a '64 Riviera (all stock), was parked for several weeks, shifted without any problems before being parked. Now it won't shift from first (out of first) to 2nd gear and will just "freewheel" without any compression or engine breaking when the rpms are increased. I have changed the fluid, the filter, added Seafoam, changed the vac modulator, checked for vacuum (18+), and removed, cleaned, and checked the governor; still won't shift? Who has any other suggestions or can offer a diagnosis?,,,
