How do you repair a transmission overdrive shifting problem on a Mercury Villager?

To repair a transmission overdrive shifting problem on a Mercury Villager, start by checking the Transmission Fluid level and condition, as low or dirty fluid can affect shifting. Inspect the throttle position sensor and vehicle speed sensor for proper function, since they are critical for overdrive operation. If those components are functioning correctly, consider examining the transmission control module for issues or performing a diagnostic scan to identify error codes. If the problem persists, it may require professional assessment or transmission rebuild.